The smallest charge can feel unfair when its reason remains deliberately hard to find.

The anger is never really about the amount. Two pounds is nothing; two pounds you cannot get an explanation for is a small message about where you stand. Opacity implies that the person paying was not expected to look, and that implication is what stings. Clarity costs the seller almost nothing, which is why its absence reads as a choice.

If a charge bothers you, ask for the reason plainly and in writing, without apologising for asking. If you set fees yourself, publish the reason next to the number. People accept a great deal when they can see why, and very little when they cannot.