A fee line

Two numbers get called fees and they have nothing to do with each other. Confusing them is behind a surprising amount of frustration, including people concluding they are being squeezed when they are looking at physics.

What it is

A charge on a transaction, from one of two unrelated sources

Where you meet it

Checkout, deposit, withdrawal

What it settles

What the number is actually paying for

Cannot tell you

Whether you are getting a good deal

The specimen

A checkout line, split by where the money goes. Lime is a business decision somebody made. Salmon is a market price nobody controls. They are usually different by an order of magnitude and they behave completely differently.

The two kinds

The pull toward larger orders

Because a fee structure usually has a component that is roughly fixed per listing, a small order carries proportionally more of it. That makes larger orders look better per unit, and the pull is genuine rather than a vendor being opportunistic.

The counterweight is that the saving is a percentage and the exposure is the whole amount, and those are not the same kind of quantity. A better unit price on an order you cannot afford to lose is not a better deal.

What a fee line cannot tell you

Whether the price is fair, whether the seller is reliable, or whether this order will arrive. It is arithmetic about a transaction and it says nothing about the transaction going well. People read a low fee as a sign of a well run operation and a high one as greed, and neither reading has anything behind it.

What to do with the number

Almost nothing. Neither figure is a decision input on a single order, because the difference between a good fee and a bad one is a fraction of a percent of what you are risking. The one place it matters is the withdrawal, where people talk themselves into leaving a balance to avoid a cost of fractions of a cent, and that is a reasoning failure rather than an arithmetic one.