[skybrian]

Yes, I agree that there are a lot of different things we can do.

However, sometimes, charging different prices based on income is impractical. Gas needs to be more expensive to discourage its use (to combat global warming), and it's not practical to ask people their income when they buy gas.

This is especially true when we're talking about prices that aren't charged to consumers directly, but will get passed on to them.

So, to avoid affecting poor people too much we need to compensate for that. The idea is that if you spend less than average on the things being discouraged then you come out ahead.