What a marketplace sale actually costs you

Ask a seller what eBay costs them and you will get a percentage. Ask what a specific eBay order netted and you usually get a pause, because the answer is not one number and it is not available in one place.

The gap between those two answers is where channel-level decisions go wrong. Not dramatically, and not on any single order, which is exactly why it survives.

The charges that stack

The headline commission is the one everybody knows. Underneath it sit several others, and which ones apply depends on the order rather than on the channel.

There are regulatory and operating charges that some marketplaces apply per order. There is the advertising rate, when the item sold through a promoted placement, which is taken on top of the commission rather than instead of it. There is payment processing. There are cross-border and currency charges when the buyer is in a different country from the listing. And there is the postage you actually paid, which is not the postage the buyer paid.

Every one of those is knowable per order. None of them is in the sale price.

Why the average does not save you

The usual workaround is an average: take last month total fees, divide by revenue, apply that percentage to everything. It gives a number that is roughly right at the channel level and wrong at every level below it.

It is wrong per product, because promoted items carry an ad rate and unpromoted ones do not. It is wrong per country, because cross-border orders carry charges domestic ones do not. It is wrong per order size, because fixed per-order charges hurt small baskets far more than large ones.

Those three distinctions are exactly the ones you would use to decide what to promote, where to sell and what minimum order value to set. The average erases all of them.

The postage number people use is the wrong one

Shipping is the most commonly mis-stated line. The figure that ends up in the calculation is usually what the buyer was charged, because that number is on the order. What you actually paid is on the carrier invoice, and it arrives weeks later with adjustments attached: surcharges for remote areas, for dimensions, for fuel.

Until the carrier invoice is reconciled back to the order, every shipping-inclusive margin figure is an estimate presented as a fact.

What changes when the fees are per order

When each charge is captured against the order that incurred it, three things become answerable that were not before.

Which products are unprofitable rather than which categories. Whether an advertising campaign paid for itself after the commission, not just against revenue. And whether a channel that looks marginal is actually marginal, or is carrying a small number of loss-making lines that could simply be delisted.

None of that requires new data. All of it is in the fee records the marketplaces already publish per order. It requires that somebody collects them and attaches them to the order rather than to the month.

Where to start

Take last month. Pick the twenty orders with the largest gap between sale price and what you believe you netted. Work out, by hand if necessary, what came out of each one.

If the answer surprises you on more than a couple of them, the problem is not your pricing.