Dossier: An Amazon Fee-Tracking Tool for Sellers

What you’re reading: a real Opportunity Dossier from our AI research pipeline — Ada spotted the signals, Bea shaped the candidates, Cora dug deep, Edie tried to kill it and owns the score, and Della wrote it up. New to our scoring? Start with How Our Star Score Works. Research date: July 2026 — facts move; check dates before betting money.

The idea: a ruthlessly accurate tool that takes Amazon’s ever-growing pile of seller fees and tells each seller their TRUE profit on every product — the honest number, not the “50% margins!” the online gurus advertise — plus an alert every time Amazon changes a fee.

Super Fluidity Deep Report · 2026-07-10

The short version

First, three quick words we’ll use a lot. A seller here means someone who sells products on Amazon’s marketplace. A SKU (say “skew”) is seller-speak for one specific product in your catalog — if you sell blue mugs and red mugs, that’s two SKUs. And FBA is “Fulfillment by Amazon”: you send Amazon your products, Amazon stores and ships them, and Amazon charges you fees for all of it.

The pain behind this idea is real, big, and loud. In one major 2026 industry survey (Marketplace Pulse’s Seller Index), 49% of active Amazon sellers named fees as their #1 profit worry, and 47% said their profit margin shrank from the year before. Add up all of Amazon’s charges — the selling fee, the FBA shipping fee, storage, ads, and a new 3.5% “fuel surcharge” — and Amazon now takes roughly 34% of everything a seller brings in. 2026 alone brought a January fee hike (about $0.08 more per unit on average, up to $0.51 more on some sizes), that 3.5% fuel surcharge starting April 17 with no end date, a new extra charge on inventory sitting unsold for 181 days (90 days sooner than the 2025 rule), and new low-stock fees applied item by item. And there’s a telling precedent: in 2022, Amazon added a “temporary” 5% surcharge — then quietly made it permanent by folding it into the regular fees. Fees only ratchet up; they never settle. That’s exactly why a stay-current tool would keep being useful. When the fuel surcharge hit the news, the stories drew big crowds on Hacker News, a busy online forum for programmers — 166 points (think upvotes) and 106 comments in 2026, and 172 points with 131 comments back in 2022. People care intensely.

But here’s the honest verdict, and it’s discouraging if you want to sell this as a standalone product. Three forces have already closed most of the gap:

Amazon built it themselves — and gives it away free. Alongside the 2026 fee changes, Amazon shipped a Profit Analytics dashboard and a per-product “Fee & Economics Preview” report, right inside every seller’s account. Sellers can now model any fee change against any product before it takes effect. For free.
Strong existing companies already sell the same thing cheap. Sellerboard ($15–19 a month), Nova Data ($29 a month), SellerQI, Helium 10, and SmartScout all already show true per-product profit, pulling the fee data automatically from a seller’s account.
Basic profit calculators are everywhere and free. Amazon has a free one. So do Helium 10, AMZScout, ProfitGuru, and FBACalc — dozens of them.

And here’s the tell. Two small independent builders launched exactly this kind of calculator on that same Hacker News forum — ProfitPilot (February 2026) and Monkey Calcs (May 2025). They got 3 points and 1 point. Enormous pain about the problem; almost zero interest in this tool as the answer.

Building the first version would take a weekend. Getting even one person to pay — against a free Amazon feature and a $19 all-in-one — is the real wall. The one piece of this that people demonstrably pay for is different: fee-error refunds. Amazon overcharges sellers by mistake (wrong weights, wrong sizes, lost items), sellers lose an estimated 1–3% of their yearly revenue to it, and services already make money finding and recovering that cash for a cut. On top of everything, the pool of sellers who buy tools is shrinking — active sellers fell from about 584,000 to about 500,000 in 14 months, and new seller sign-ups are at a ten-year low.

Bottom line up front: don’t build this as a standalone paid tool. If you touch it at all, give the calculator away free as a way to attract sellers, and make your money on the refund-recovery side.

The scorecard

Each pillar is scored 0 to 5. Higher is better.

What we measured	Score /5	Why
How fast can you learn the truth?	4	The best thing about this idea: a hand-made “Fee Truth Report” for 5–10 real sellers can give you a clear yes-or-no in under 2 weeks for well under $500. But it takes real sellers handing over their data and paying — not just a sign-up page.
How fast can you build the first version?	5	One person, one weekend. Which is exactly the problem — anyone can.
How fast to a first paying customer?	2	The demand is loud, but every sales conversation hits “Amazon already shows me this free” or “my $15 Sellerboard already does it.” Remember those forum launches: 1 and 3 points.
How much money do you need?	5	A laptop and well under $1,000. No inventory, no employees, and Amazon’s official data connection for outside software (called SP-API) is free to use.
How hard is it to run?	3	The math itself is simple, but everything depends on rules Amazon controls and can change without warning. Awkward, not fatal.
How crowded is it?	1	About as crowded as it gets: Amazon gives the core value away free (covering 34 fee types, product by product), and established companies bundle the rest.
Is the market growing?	2	Split answer. The problem keeps growing (fees keep rising). But the number of sellers who’d buy the tool is shrinking — 584,000 down to 500,000 active sellers in 14 months, new sign-ups at a decade low.
Does AI give you an edge?	1	No. This is straightforward fee arithmetic. Worse, AI makes the calculator so easy for anyone to build that it destroys what little edge existed.
Do you have a moat?	0	Fatal. A moat is anything that makes your business hard to copy, like a castle’s water ditch. This has none: it’s a weekend clone, you own no special data, and you’re completely at the mercy of one platform — which now gives the exact same thing away free.

Overall Fluidity Rating: ★☆☆☆☆ (1/5)

What that means: One star — poor. The case against outweighs the case for. Yes, you can test it fast and cheap, and yes, it costs almost nothing to build. But those virtues just mean you’ll cheaply confirm a “no.” The moat score is a fatal zero: the platform ships the core value free, a $15 competitor already delivers the exact “true profit” promise, and the tool itself is a weekend copy with no special data — all while the pool of tool-buying sellers shrinks. Under our rules, a single fatal zero drags the whole score to the floor no matter how good the other numbers look. The only version people clearly pay for — recovering fee overcharges for a cut of the refund — is a different, labor-heavy, already-crowded business, not this product. Don’t build the standalone tool. If you engage at all, run the free calculator as a front door and make money on the refund side.

Who this is for (and who it isn’t)

We score every idea three times, once for each kind of founder:

Kind of founder	Adjusted score	The honest read
A — The solo coder (can build anything, has no audience)	★☆☆☆☆ (1/5)	No lift at all. Your strengths — fast coding, AI help — attack the part that was never the problem, because the build is already a weekend. Your weakness — nobody knows you — is exactly the wall: reaching sellers and getting them to pay against a free Amazon feature. You’d ship it in a weekend and get the same silence those forum launches got. The only sensible use is as a free portfolio piece, not a business.
B — The organizer (great at running operations, doesn’t code)	★★☆☆☆ (2/5)	A modest lift — and the best fit for the only version people pay for. The fee-refund business is paperwork, process, and follow-through, with proven pricing (services keep roughly 15–25% of the money they recover, and the seller pays nothing unless money comes back). That’s squarely your kind of work, and you don’t need to code it. But it’s a crowded field (GETIDA, Refunzo, SellerQI already do it) — and it’s a different business than the one on the label.
C — The person with an audience (already has a trusted crowd of sellers)	★★★☆☆ (3/5)	The biggest lift, because you’ve already solved the one genuinely hard part: reaching people. Amazon’s constant fee changes generate constant searching and worrying — perfect fuel for a newsletter. The free calculator plus fee-change alerts becomes the engine; the money comes from the attention (referral commissions to Sellerboard or GETIDA, sponsors, sending leads to refund services) rather than from the commoditized tool. Real, but contested — and it only works because of the audience you already built.

The idea in plain words

Amazon’s fees pile up quietly: the selling fee, the FBA shipping fee, storage, ads, and now a 3.5% fuel surcharge — together taking roughly 34 cents of every dollar a seller brings in. This tool would compute each seller’s true profit on every product after every current fee, and translate each newly announced fee change into plain dollars: “this new surcharge costs you $0.42 on this mug.” It replaces the gurus’ advertised 50% margins with the honest number. The pain behind it is thoroughly documented and intensely felt. The question this report answers is whether that pain turns into a business someone should build — and the evidence says no.

The pain is real

Fees creep, they don’t jump — “never one dramatic hike, always another 50 cents here, another 1% there” — so sellers only notice their profit eroding after the fact. A brand selling $1 million a year now sends about $340,000 to Amazon — roughly $80,000 a year more than in 2020.
49% of active sellers rank fees as their #1 profit concern; 47% report a year-over-year margin decline (Marketplace Pulse 2026 Seller Index).
Amazon announces each fee change as dense official text. Translating “3.5% fuel surcharge” or “181-day aged-inventory fee” into actual dollars across your real catalog is manual, tedious, and easy to get wrong.
The guru courses advertise 50%+ margins. Real sellers, after product costs, all the fees, and ads, net more like 15–20%. People price their products on fantasy numbers.
Amazon charges more than 40 distinct fee types; most tools only track 15–25 of them, so even the paid dashboards undercount the true cost.
Sellers lose an estimated 1–3% of yearly revenue to Amazon’s own mistakes — wrong weights, wrong dimensions, mishandled returns — that Amazon never flags. Claiming the money back is a manual process with a 60–120 day wait (sometimes up to 18 months).
And sellers can’t just leave: of the sellers most upset about fees, only 24% are shrinking their Amazon business while 42% are still growing it. They’re stuck managing the fee pile, not escaping it.

Who you’d be up against

Competitor	Price	What you need to know
Amazon itself (Profit Analytics + Fee & Economics Preview + free Revenue Calculator)	Free, built into every seller account	The single biggest threat. Amazon launched a profit dashboard AND a per-product fee preview report alongside the 2026 changes, specifically so sellers can model the fuel surcharge and every other fee change against any product before it goes live. That’s this idea’s core value — shipped free, by the company that owns all the data.
Sellerboard	$15/mo (paid yearly) or $19/mo, rising to $63/mo at 50,000 orders	The category leader for true profit. Connects to a seller’s account automatically and itemizes every fee — selling, FBA, storage, returns — per product, in real time. Also tracks refund claims.
Nova Data	$29/mo (paid yearly), 14-day free trial	Per-product profit at three levels of depth, after every Amazon fee, ads, product costs, and returns — benchmarked against 2026 category averages across 21 marketplaces. Also has its own Amazon refund tracker.
SellerQI	Free basic version; paid refund service	Scans 18 months of a seller’s FBA transactions to find overcharged fees, lost units, and return errors. Strong on exactly the money-recovery angle.
Helium 10	Free calculator; full toolkits $39–$399/mo	Their free calculator alone kills any pricing power on a standalone one; the paid version covers profit and fee tracking as part of a full suite.
Refund-recovery services (GETIDA, Refunzo, fbarefunds, Aura)	No upfront fee — they keep ~15–25% of whatever money they recover	Proven, painless pricing tied directly to fee overcharges. They typically recover 2–5% of a seller’s FBA costs.
The indie calculators (ProfitPilot, Monkey Calcs)	Free	Launched on Hacker News in Feb 2026 (3 points) and May 2025 (1 point). They prove the pain is felt — and equally prove a standalone calculator gets no pull.

The gaps that are actually open

True completeness. Covering ALL 40+ fee types when most tools cover 15–25 is a real, checkable difference — but hard to market, because a buyer can’t easily verify who’s more complete.
Forward-looking alerts. “This new surcharge just pushed 14 of your products below breakeven” — the existing tools show you today’s profit but aren’t built around warning you about newly announced fee changes. Even Amazon’s own preview is passive: the seller has to go look.
The honesty angle. “Your real margin vs. the guru’s advertised 50%” is a marketing and education story no competitor leans into.
The newest fees. The 181-day aged-inventory charge, warehouse-and-distribution storage fees, and returns-processing fees are newer and less well modeled by the older tools.
The refund-recovery side has clearer proof that people pay than the calculator does, and it’s only partially bundled into the existing tools.

What’s happening in this market

Lots of attention, lots of pain — but the market is shrinking and the product is becoming a commodity. Roughly 1.9 million sellers are active on Amazon worldwide. Independent sellers moved about $305 billion of goods in the U.S. in 2025 (out of $575 billion globally), and Amazon collected $172.2 billion in seller fees and services that year. Fees and ads are now about a third of Amazon’s entire company revenue — so Amazon has every reason to keep raising them, which keeps a fee tool permanently relevant.

But the customer pool is contracting. Active sellers fell from about 584,000 (January 2025) to about 500,000 (March 2026). New seller sign-ups hit a ten-year low — about 165,000 in 2025, down 44% from the 2020 peak. And the money is concentrating: fewer than 8,000 sellers now generate half of all U.S. independent-seller sales, down from about 15,000. The sellers left standing are the big ones — who already run full paid suites like Sellerboard and Helium 10.

So: momentum on the problem is real (three-plus fee actions in 2026 alone, 166–172-point forum threads). Momentum on standalone fee tools is weak (1–3 point launches, free calculators everywhere, and Amazon shipping its own previews).

If you did it anyway, here’s how

Do not launch this as a $9–19/month subscription calculator — it’s boxed in between Amazon’s free tools and Sellerboard’s $19 everything-included. If you pursue it at all, flip it:

Give the calculator away free — the most accurate, most current one, with fee-change alerts. It’s the front door: every Amazon fee change sends worried sellers searching, and they find you.
Make the money on refund recovery, where people provably pay: audit sellers’ accounts for products Amazon overcharged (wrong weight, wrong size, botched returns) and keep roughly 15–25% of whatever you recover. The seller pays nothing unless money comes back.
Optionally, sell bigger sellers and agencies a bulk “true margin across your whole catalog, plus the lowest price you can safely charge” report.

Honestly, that’s a newsletter-plus-tool side business or a services business — not the kind of fast-growing software company investors chase.

The marketing plan (make it before you build)

Let’s be straight before we get into tactics: this is a one-star idea, and no marketing plan changes that. Marketing can’t rescue a product with no moat — it just helps you lose money faster, in front of more people. So this is not a growth plan for a $9–19-a-month subscription calculator. There isn’t one. What follows is the only path with a chance if you build anyway: the flipped model from the section above — the calculator given away free as a front door, with the money made on refund recovery. Everything below markets that version, because the subscription version has nothing to market.

Two numbers tell you the whole problem. For software sold to small e-commerce businesses — this exact niche — getting one paying customer costs about $300 in marketing money, on average (First Page Sage’s 2025 B2B software report; that’s your total marketing spend divided by the customers it actually wins you). Now hold that against what you could charge: Sellerboard is $15–19 a month, and Amazon is free. Spend $300 to win a $15-a-month customer and you wait a year and a half just to get your money back — if they stay, and if they never notice the free version. That math never closes. A refund-recovery client is a different animal: recovery services find 2–5% of a seller’s FBA costs and keep 15–25% of it, so one mid-sized client can be worth hundreds or even thousands of dollars. That’s the only money in this whole idea that can pay a marketing bill.

Before you build anything

The cheap test in the next section — hand-making “Fee Truth Reports” for 5–10 real sellers and asking them to pre-pay — isn’t just a test. It’s your first marketing. If nobody pays, you got your “no” cheap. If people do pay, you get three things at once: your first paying customers, your first word-of-mouth lines (“this report found $1,400 Amazon owed me”), and the exact words sellers use to describe the pain — which become your copy. Run the test where sellers already hang out. The big seller Facebook groups are genuinely huge: Helium 10’s members group tops 70,000 sellers and MySilentTeam runs about 79,000 (Helium 10’s own community pages; Lab 916’s seller-forum roundup).

Two more moves before you launch, both free:

Start the fee-alert list now, before the product exists. One page: “we email you the dollar impact of every Amazon fee change.” Costs nothing, and it tests the alert idea on its own, apart from the calculator.
Talk to partners early. Seller-focused bookkeepers, prep centers, and accountants see fee pain every day but don’t do refund recovery. The pitch is easy because they risk nothing: “free money for your clients; you get a cut.” The incumbents already prove this works — GETIDA pays its referral partners 10% of the recovery fee for the first 12 months (GETIDA’s own partner program page).

The three ways you’d actually reach people

1. Be there the morning Amazon announces a fee. Every fee announcement sends thousands of worried sellers searching within hours — the dossier’s own evidence is the 166-point forum threads. And fee changes are scheduled: Amazon announces them ahead of time. So you can have the plain-dollar translation (“here’s what the 3.5% surcharge costs on a $24 mug”) written and posted the morning the news breaks, with the free calculator attached. This works because you’re not building an audience from nothing — you’re catching people who are already looking, at the exact moment it hurts, and nobody currently owns the “translated into your dollars, same day” angle. Cost: your hours, roughly $0 cash.

2. Work the seller groups by hand. The Facebook groups and seller Slacks above are where the kill test already ran. The move that fits this product isn’t posting links — it’s making the product’s output the post: personalized one-page Fee Truth Reports, offered free, one seller at a time. High effort, zero dollars, and it sells because the report is the demo, the audit, and the refund-recovery pitch all at once (“we also found $900 in fee errors — want us to file the claims?”).

3. Let partners send you clients. Bookkeepers, prep centers, agencies, and accountants already have the trust and the client list you don’t. Offer them the GETIDA-style deal — a cut of recovered money, client pays nothing up front. This works because it borrows someone else’s audience instead of building your own, which matters a lot in a niche where every trusted voice is already paid for (more on that below).

What a customer really costs you

How you reach them	What it really costs	The honest math
Same-day fee-news posts	Your hours; ~$0 cash	Guess: a few hours per fee announcement. These get you free sign-ups, not customers — free products turn roughly 3–5% of free users into paying ones on average (First Page Sage’s freemium numbers), so figure about 1 paying refund client per 20–30 people who sign up and stick around.
Hand-made reports in the groups	2–4 of your hours per report; $0 cash	A guess. If the kill test’s pattern holds, most will say “Amazon shows me this free” — the ones who don’t are your refund-recovery leads.
Partner referrals	10% of recovered money, paid only when money comes back	GETIDA’s own partner rate — proven pricing in this exact niche. Cold emails to reach partners get replies maybe 1–5% of the time (Belkins’ 2025 cold-email study), so expect 30–50 emails per real conversation.
Paid search ads (just so you see it)	About $5.26 per click, averaged across industries (WordStream’s 2025 Google Ads benchmarks); business-software keywords often cost more	Guess: if a few percent of clicks become free users, and 3–5% of those ever pay, one paying customer costs well over $1,000. Never workable at this price.

One thing a day, every day

Here’s the part most plans skip. My friend Andrew Kaplan — a guest on my LOA Today podcast — wrote a book called The Last Law Of Attraction Book You Will Ever Need To Read. That’s about as crowded a market as exists on this earth. Over roughly five years, he’s sold about 175,000 copies. I asked him how. He said: “Every single day I do at least one thing in service of the book: write a post, do a podcast, make a YouTube video, post a short on TikTok, give a talk, do a radio show … at least one thing every day, 365 days a year.”

That’s the whole secret, and it’s the thing nobody wants to hear: marketing isn’t a launch event. It’s one thing a day, every day, forever. For this business, your one thing a day looks like:

Write the plain-dollar breakdown of whatever fee change Amazon announced this morning.
Hand-make one Fee Truth Report for one seller in one of the big Facebook groups.
Send five partner emails to bookkeepers or prep centers.
Answer one fee question in the Helium 10 or MySilentTeam group — actually answer it, with numbers.
Add one name to the fee-alert list by asking one seller if they want the dollar impact emailed to them.
Follow up with one seller whose report found errors: “want us to file the claims?”
Post one before-and-after from a real recovery (with permission): “Amazon owed this seller $1,400.”

Now be honest about what that list costs, because this drumbeat is the recurring price of the business. It’s not a launch-week sprint — it’s a daily payment, in your hours, for as long as the business lives. Count it before you commit, the same way you’d count rent.

Your first three months

Days 1–14: run the kill test — 5–10 hand-made reports, ask for pre-payment. This is your test and your first marketing at the same time. If nobody pays, stop here; that was the point.
Weeks 3–6: ship the free calculator and the fee-alert list. Post your first same-day fee-change breakdown (2026 has reliably served up at least one fee action per quarter to react to). Offer the personalized reports in two or three of the big seller groups.
Weeks 7–12: run the refund-recovery audits for whoever paid in the kill test — that’s your proof the money is real. Meanwhile, send the partner pitch to 50–100 seller-service businesses (at 1–5% replies, that’s 1–5 real conversations).
Day 90: count paying refund clients and recovered dollars. If the number is zero or close to it, the kill signal fired late — but it fired. Stop.

Don’t waste money on these

Paid ads, anywhere. At $5.26 average per click (WordStream), against a competitor whose price is free and an incumbent at $15 a month, no ad ever pays for itself. Ads only work when each customer brings in enough to cover them — and the calculator brings in zero by design.
Conference booths. The Prosper Show is the natural spot — over 1,200 sellers, 170+ service providers (Prosper’s own show pages) — but exhibit-industry budgeting guides put a first-time 10-by-10 booth at $15,000–$40,000 all-in (AMW Group’s trade-show pricing guide). That’s this whole business’s budget, several times over, for one weekend.
Paying the seller YouTubers and newsletters. Niche business newsletters charge roughly $50–$150 per thousand readers (Paved’s and beehiiv’s sponsorship benchmarks), and mid-sized YouTube channels charge $200–$5,000 per sponsored video (Influencer Marketing Hub’s 2026 rate guide). And worse than the price: those voices are already spoken for. Helium 10 pays its affiliates 100–125% of a referred customer’s first month plus ongoing cuts (Helium 10’s affiliate page), and Sellerboard pays 20% ongoing for up to six years (Sellerboard’s partner page). Everyone sellers trust already earns more recommending your competitors than you could ever pay them.
Trying to rank in Google for “Amazon FBA calculator.” The first page is Amazon itself, Helium 10, AMZScout, and a dozen established free clones. A new site loses that fight on age and authority alone. The only search you can win is the news — freshly announced fee changes, where fast and specific beats established.
Cold-emailing individual sellers. A 1–5% reply rate is fine when one reply is worth thousands. It’s a treadmill when the product is free and the money shows up later, maybe. Save cold email for partners, where one reply opens a whole pipeline.

So here’s the honest summary: everything that costs money is ruled out by the product’s zero price, and everything that’s free costs your hours — one thing a day, every day — which this one-star idea probably doesn’t deserve. That’s not a marketing problem. That’s the verdict, restated. And one last rule: this plan is a draft until real customers vote. Once you’re live, come back and rewrite it against what actually happened — plan the marketing, build, market, test, then revisit the plan.

The first version to build

Step 0 (days, no code): Hand-make a “Fee Truth Report” for 3–5 real sellers. Take their Amazon fee-preview file or catalog spreadsheet, compute true profit per product after every 2026 fee change, and flag which products the fuel surcharge and the aged-inventory fee pushed below breakeven. Measure two things: will they pay for the answer, and does the error-hunt find real money?

Step 1 (a weekend): A free web tool that reads a seller’s fee report (or connects read-only through Amazon’s official data plug), models every current and newly announced fee per product, and emails an alert whenever Amazon announces a fee change — with each product’s projected dollar hit and new margin.

Step 2 (only if Step 0 proved people pay): Add the refund-recovery audit — scan transaction history for overcharges, then file and track the claims. Do not write this code before Step 0 proves the money is real.

The cheap test that settles it

Within one week, for roughly $0: find 5–10 real Amazon sellers in a seller Slack group, Facebook group, or on Hacker News. Hand-build each one a one-page “Fee Truth Report” from their own fee-preview file — true profit per product, and which products the 3.5% fuel surcharge plus the 181-day inventory fee pushed below breakeven. Then ask them to pre-pay a small amount for ongoing alerts.

The kill signal is explicit — and likely: they say “Amazon’s own dashboard / my Sellerboard already shows me this,” or they simply won’t pay. That tests the exact question the whole idea hangs on — will anyone pay when the free version exists? — before you write a single line of code.

How sure are we? Very sure on the core read. The two decisive kill facts — Amazon’s free profit dashboard and fee preview covering 34 fee types product-by-product, and Sellerboard delivering the same “truth layer” at $15 a month — were independently verified on the open web and match or exceed what the research claimed.

The risks

Amazon eats you (the biggest one): Amazon shipped its free profit dashboard and fee preview alongside the 2026 fee changes. The platform is actively closing this exact gap, and it owns the true data.
The existing companies absorb you: Sellerboard ($19) and Nova ($29) already deliver per-product true profit AND refund tracking. They could add a fee-alert feature overnight.
No pricing power: profit calculators are free everywhere — Amazon, Helium 10, AMZScout. You cannot charge for the headline feature.
You live on Amazon’s terms: access to seller data, usage limits, and the rules for automated refund claims are all Amazon-controlled and can change without notice — as the fees themselves keep proving.
A shrinking, concentrating customer pool: fewer sellers each year, with the money pooling into big sellers who already own full suites.
Demonstrated indifference: despite massive pain (166+ point forum threads about the problem), standalone fee tools launched to 1–3 points. Attention to the problem does not convert into paying for this tool.
“We’re more accurate” is hard to prove: a buyer can’t easily check whether your tool tracks 40 fees and a rival’s tracks 22.

Why we’d tell you not to build this

Amazon already gives the core value away free: a native profit dashboard and a per-product fee preview that model any fee change before it takes effect — released with the very 2026 fee changes this idea is built on.
The strongest competitor, Sellerboard ($15–19/month), already does “real net profit per product after every fee, in real time” — the exact promise of this tool — at a price a narrow tool can’t profitably undercut.
The idea’s own proof-of-pain is actually proof of no pull: ProfitPilot got 3 points, Monkey Calcs got 1. Sellers feel the fee pain intensely (166+ point threads) but do not rally to standalone calculators.
Basic profit calculation is fully commoditized — Amazon’s free calculator plus a dozen free clones — leaving zero pricing power on the headline feature.
The customer pool is shrinking (about 584,000 → 500,000 active sellers in 14 months; new sign-ups at a decade low) and concentrating into big sellers who already own full paid suites.
The founder-time verdict: building it is trivially fast, but getting paid and staying uncopied are both poor. You’d spend months competing on a free, commoditized feature against both the platform itself and $19 competitors. The one version people clearly pay for — recovering fee overcharges for a cut — is a different, labor-heavy business already served by Refunzo, GETIDA, and SellerQI.

Sources

Marketplace Pulse — The Paradoxical Dependence of Amazon & Its Sellers (the 2026 Seller Index: 49% name fees the #1 concern, 47% margin decline, the 24%-vs-42% “stuck sellers” split, and the 584k→500k seller count)
CNBC — Amazon adds 3.5% fuel and logistics surcharge for sellers (the Hacker News thread: 166 points, 106 comments)
Supply Chain Dive — Amazon to apply 3.5% fuel and logistics surcharge on fulfillment
Kavout — What’s Driving Amazon’s New Surcharge, and Is It Just Temporary (the 2022 “temporary” 5% surcharge that quietly became permanent)
Mike Begg — Amazon Seller Fees 2026: 34% Take Rate Crushes FBA Margins
Amazon Selling Partners — Official Update to U.S. Referral and FBA fees for 2026 (Amazon’s own free Profit Analytics + Fee & Economics Preview)
Seller Labs — Amazon Fee Increases 2026: How to Protect Profit (Amazon’s built-in fee-preview tools, product-by-product impact)
Sellerboard Review 2026 — BagEngine (real net profit per product, automatic fee capture, pricing)
Sellerboard vs Helium 10 — vovaeven (pricing tiers: $15–63/mo vs. $39–399/mo)
Nova Data — Amazon FBA Profit Margin Calculator ($29/mo, per-product profit at three depths)
Nova Data — Amazon Reimbursement Tracker (the fee-overcharge refund angle)
SellerQI — Amazon FBA Reimbursement Tool (scans 18 months of transactions for overcharged fees)
Refunzo — Amazon FBA Fee Errors: Detection and Resolution Guide (1–3% of revenue lost to fee errors; 20% of items misclassified)
AMZ Prep — Amazon FBA Fees 2026: Full Breakdown + April 17 Surcharge Update
eFulfillment Service — Amazon 2026 FBA Fee Changes (the 181-day aged-inventory tiers and item-level low-stock fees)
Show HN: ProfitPilot — pricing calculator for marketplace sellers (Feb 27, 2026 — 3 points)
Show HN: Monkey Calcs — Amazon profit calculator (May 23, 2025 — 1 point)
AMZ Prep — Amazon Marketplace Seller Statistics 2026 (~1.9M active sellers worldwide; new registrations at a decade low)

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