The sources
Link-out only. Central banks, competition regulators and published rate cards. No vendors, no affiliates, nothing sponsored.
Payments: the only layer a regulator made public
Card fees are the best-documented part of the stack, because several central banks forced disclosure. Start here, because it is the one number you can actually check rather than infer.
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Average debit card interchange fees
The Fed publishes average interchange per transaction under Regulation II. An actual measured average across the market rather than a rate card, which makes it the single most useful number in the whole stack.
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Regulation II data collections
The underlying biennial collections behind that average, including issuer costs and fraud losses. Dry, and the closest thing to ground truth on what moving money actually costs.
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Visa Rules
The network's own published rules and rates. Published by an interested party, so treat it as the list price rather than what anyone pays.
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Payments System Board
Australia capped interchange years before most regulators moved, so its published analysis is the closest thing to a natural experiment on what happens when the fee is forced down.
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Bank for International Settlements
Cross-border payments research. Useful if you sell internationally, where the stack gets meaningfully more expensive and much less transparent.
Platforms: list price is not the take rate
Every marketplace publishes a fee schedule. None of them is what a seller actually pays once advertising, fulfilment and storage are included. The published card is where you start, not where you finish.
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Selling on Amazon fees
Referral fees by category, fulfilment and storage. The published schedule, from the party charging it. What it omits is how much of a seller's revenue ends up going back to the same company as advertising.
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Seller fees
Final value fees by category. Simpler than Amazon's and easier to reason about.
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Pricing
Subscription plus payment processing plus the app stack, which is the part that quietly compounds. The platform fee is rarely the largest line by the end of a year.
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Pricing
Published processing rates. Worth comparing against the Fed's measured average above: the gap between the two is the processor's margin.
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Business fees
Another published card. Included so the comparison is against more than one processor.
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Annual reports
Where the real number lives. A public marketplace discloses seller-services revenue and gross merchandise volume; dividing one by the other gives a blended effective take rate that no rate card will tell you.
Regulators, who publish what the platforms will not
Competition authorities run investigations that force disclosure. Their findings are free, detailed, and written by people with subpoena power rather than a media kit.
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CMA cases
Live and closed UK market investigations. The market studies in particular contain fee and margin detail that exists nowhere else in public.
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Digital Markets Act
The EU rules governing designated gatekeeper platforms, including obligations on self-preferencing and on what they may charge. The compliance reports are the interesting part.
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Competition enforcement
Case filings and enforcement actions. Complaints against large platforms often set out fee mechanics in detail, because that is the alleged harm.
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Antitrust Division
The other US enforcer. Filings here are dense and specific about how money moves between parties.
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Consumer Financial Protection Bureau
Payments and consumer credit. Relevant to buy-now-pay-later and to the fees attached to it, which sit outside the usual card analysis.
How to read a take rate
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Online advertising and marketing guidance
What must be disclosed in advertising, including affiliate relationships. Worth reading precisely because so much of the ecommerce information layer does not comply with it.
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The Nilson Report
The long-standing payments industry data source. Subscription, and named here because it is what the industry itself cites when a free number is not available.