Where our numbers come from — and how to check them yourself

Click any fee in your analysis. You'll see the number, the published page it came from, and the date we last checked it. Click the link. Read the page. Check the number matches. That's it. We're not asking you to trust us. We're giving you the tools to verify us.

This page shows you how.

Where our numbers come from

FBA Fulfilment Fee
Large standard, 12+ to 16 oz, non-apparel
$10–$50 price band, 2026 non-peak
Rate $4.60

Source: sellercentral.amazon.com/help/…

Verified: 18 April 2026

View source page →

Every fee record in the database traces to a specific published page. Click the source link. Read the page. Check the number matches. We're not asking you to trust us. We're giving you the tools to verify us.

We monitor 1,257 source URLs for changes. When a rate card updates, every affected analysis recomputes automatically — you see the impact before your next login.

This is not a sample. 8,938 fee records across Amazon, eBay, Walmart, and Shopify — every rate, every tier, every weight band, every marketplace. Each one sourced. Each one verifiable.

Two kinds of accurate

Some tools compute your profit from what the platform's API reports. The calculation can be precise. The input can still be wrong.

If the platform misclassifies your product, applies the wrong fee tier, or charges a rate that doesn't match its published schedule — the API reports the wrong number. The tool faithfully computes with the wrong number. The profit calculation looks precise. It isn't accurate.

We start from a different place. Your fees are computed from each platform's published rate cards — the same documents the platform is contractually obligated to follow.

API-based tools
Platform charges fee
API reports charge
Tool computes profit
If the platform was wrong, the tool is wrong too. Nobody checks.
FineMargins
Platform publishes rate card
FineMargins extracts the rate
FineMargins computes the expected fee
Compares against the actual charge
Flags every difference. Source linked.

Don't take our word for it

Copy this into ChatGPT, Claude, or whichever AI you use:

"If a profit analytics tool computes my margins from the same API data the platform provides, can it detect when the platform has charged me incorrectly? What would I need to catch fee errors — the platform's own data, or an independent source?"

See what it tells you.

How deep does this go

8,938
fee rates. Every one sourced.
Not "Amazon charges about 15%." The specific rate for your category, your weight band, your size tier, your price point, your marketplace.
26
marketplaces. Each extracted independently.
Amazon UK's FBA rate comes from Amazon UK's rate card. Not estimated from the US rate with a currency conversion.
1,257
source pages. Every rate traced to one.
Every number links to the published page it came from. Click through and check it against ours.

From calculation to verification

We compute what the published rate card says each fee should be. But we can go further — upload your settlement report and we check every fee line independently.

How settlement reconciliation works →

Verify us yourself

One product. Every fee. Every source linked. Click any number and check it against the published page. If you find one that doesn't match — tell us. We'll fix it and update the source trail.

See it in action → · Five sellers, $2,360 to $29,352 each →

Go deeper

Amazon fees → · eBay fees → · Walmart fees → · Shopify fees →

Every number from published platform rate cards. Every source linked. Every calculation reproducible. About the person behind this →

Rates verified 25 June 2026.