The shipping you charge is not shipping you keep

The question

You list an item at $50.00 and charge the buyer $10.00 for postage. The buyer pays $60.00. You then hand most of that $10.00 straight to a carrier, so it never really was your money.

Does the platform take its cut of $50.00, or of $60.00? On most marketplaces the answer is the second one, and it is the single most common error in competing fee calculators — which quietly understates every shipped order.

Measured, not asserted

Below, the same order is priced twice on each platform: once with no shipping, once with $10.00 of buyer-paid shipping, on default settings. The difference is what that shipping cost you in fees.

What the spread means

On Amazon, $10.00 of buyer-paid shipping generates $1.50 in fees, or 15% of it. On Poshmark and Vinted it generates nothing at all. Same order, same buyer, same postage — 6 of the 8 platforms here bill you for it and 2 do not.

The practical consequence is that shipping is not a neutral pass-through. Raising what you charge for postage raises your fee bill on most marketplaces, so “free shipping, higher item price” and “lower item price, buyer pays postage” are not the same trade — the second costs you more on any platform in the top half of that table.

Platforms this question does not apply to

The table above covers only platforms where the seller sets a shipping price the buyer pays. The rest of the database is left out on purpose, because running the same measurement on them would produce a number with nothing behind it:

• Stripe, PayPal, Square. Payment processors charge on whatever total passes through them, so shipping is inside the amount by definition. There is no separate marketplace shipping charge to measure.
• Gumroad, Lemon Squeezy. Digital goods. Nothing is posted, so there is no shipping to charge for.
• Fiverr, Upwork. Freelance services rather than physical goods. A shipping figure here would be a number with nothing behind it.
• StockX. StockX routes the item through its own verification centre rather than letting the seller set a buyer shipping price, so the question does not arise in the same form.

What this does not settle

It does not tell you how to price. Free shipping affects whether an item sells at all, and on some marketplaces it affects search placement too. Those effects are real and are not fee arithmetic, so this site has nothing to say about them.

It also uses default settings and United States rates. Several of these platforms price shipping differently by country or by plan, and each calculator names its own variations rather than choosing one silently. The full schedules, with sources and the dates they were read, are on fee schedules.