Marketplace fees are almost never a single percentage. They are a percentage of the total the customer pays. Shipping included; plus a fixed amount per order, and often a listing charge and a payment fee on top. At 10 per cent plus 0.30 on a 50 sale, fees are 5.30 and the effective rate is 10.6 per cent. On a 5 sale the same structure is 16 per cent.
That is the first thing to work out about any platform: what the fixed component does to your basket size, because it is invisible in the headline rate.
What does each platform actually charge?
The structures differ more than the percentages do, which is why comparing headline rates alone is misleading.
| Platform | Structure |
|---|---|
| eBay | Final value fee on the full amount including shipping, plus a fixed per-order fee |
| Etsy | Listing fee per item, transaction fee on the total including shipping, payment processing on top |
| Amazon FBA | Referral fee as a percentage, plus a fulfilment fee, plus storage |
| Own store | Payment processing plus apps, with acquisition cost in place of commission |
The commission does not disappear when you leave a marketplace, it changes name. A Shopify store pays no referral fee and pays for its own traffic instead, and on a paid-acquisition store that cost is usually larger than any marketplace commission.
Which costs get left out?
Four, consistently, and each one is large enough to turn a positive unit economic negative.
- Advertising. On Amazon an ACoS of 20 per cent on a 30 item is 6 a unit, comfortably more than the referral fee. Promoted listings on eBay work the same way.
- Returns. A return costs the outbound shipping, the inbound shipping and often the item, and the rate is a property of the category rather than of your listing.
- Storage. Long-term storage fees are a quiet drain on stock that does not move.
- Your own labour. A handmade item taking ninety minutes for twelve of margin pays eight an hour before any allowance for photography, admin or messages.
How do you work out the real number?
Contribution per order, which is the order value less everything that varies with it: goods, fulfilment, payment fees and acquisition. A 75 order with 28 of goods, 7 of fulfilment, 3.4 per cent fees and 12 of acquisition contributes about 25.45: a 33.9 per cent contribution margin.
That figure answers the only question that matters at the unit level: does one more order make money? Volume does nothing to repair a negative answer; it only multiplies it, and it does so while the revenue chart points encouragingly upwards. That is the specific way an e-commerce business can look like it is working right until the moment external funding stops and the arithmetic becomes visible.
Why does the fixed fee matter so much?
Because it is a constant against a variable. The fixed component does not scale, so its weight is entirely a function of basket size: the same 0.30 is a rounding error on a 50 order and a tenth of the margin on a 5 one. That single fact reorders the platform league table depending on what you sell. A low percentage paired with a high fixed fee flatters a business with large baskets and quietly punishes one selling small items, and a marketplace comparison that ignores basket size is comparing nothing.
The practical consequence is that platform choice and product choice interact. Selling 8 accessories on a platform optimised for 80 orders is a structural disadvantage no amount of listing optimisation fixes, and raising the average basket is often a better response than switching platform.
Contribution is also the right basis for deciding what to promote. Two products with the same price and the same percentage margin can contribute very differently once fulfilment and return rates differ, and a bulky low-value item frequently contributes less than a small expensive one that looks worse on paper.
What is the honest comparison between own store and marketplace?
Total cost per order, with acquisition included on both sides. A marketplace charges a commission and supplies demand; a store charges nothing and you buy the demand yourself.
The marketplace usually wins on cost per first order and loses on repeat, because the customer relationship belongs to the platform. A store that cannot generate repeat purchases is paying acquisition every time and has the worst of both structures.
Questions people ask
Do fees apply to shipping? On most marketplaces, yes; the fee is charged on the total the buyer pays. Charging shipping separately does not avoid the commission on it.
Is the effective rate worth calculating? Always. It folds the fixed fee into the percentage at your actual order value and makes two platforms comparable in one number.
Should advertising go in the fee calculation? In the unit economics, yes. It is a variable cost per order in everything but name, and leaving it out is the single most common reason a seller believes a product is profitable when it is not.
What about VAT? Fees are usually charged on the gross the buyer paid, and your margin must be worked out on ex-VAT figures. Mixing the two inflates the apparent margin by the whole VAT rate.
Do fees change with volume? On several platforms, yes — tiered rates, subscription plans that lower the per-order fee, and category-specific referral rates all exist. Modelling at your actual volume rather than the published headline is the only way to compare them.
Work out the effective rate at your basket size, then take contribution per order rather than a percentage. The marketplace fee calculator handles any percentage-plus-fixed structure, and carries the Etsy, Amazon FBA and Shopify shapes of it along with the plain own-store order, since a marketplace fee schedule is a set of numbers rather than a different sum. The eBay fee calculator models that platform on its own.