Why does one of these scenarios seem unfair while the second seems reasonably fair?

Vendors raise soda prices in heat wave.

Vendors lower soda prices in winter.

These could be describing exactly the same real world scenario.

The simple answer is of course that we identify more casually with the buyers rather than the sellers, so that falling prices are good news and rising prices are bad news; but I think there is a third bit and that’s what makes it not just good/bad news but adds an element of fairness, an ethical element.

The first story suggests that the vendors are taking advantage of a misfortune that has befallen their customers. Turning another’s misfortune into your profit doesn’t seem too strong on the ethics.

When thinking about the ethical puzzles around discriminatory pricing “don’t take advantage of other’s misfortune” seem to be a useful rule of thumb. For example if your discriminatory pricing takes advantage of the febbleminded it is more likely that society will sanction you.

Puzzling out good ethics about this stuff isn’t just about being able to show your face in polite company. It’s also about maintaining people’s trust – which lowers your negotiation costs.