The problem here is how justifiable is the change in prices, not the amount. If you raise prices because you really have to and I can't keep up, that's OK, that means that my business is not viable anymore, I need to charge more also or cut on expanses (or go out of business, which is also OK). But if you keep milking me for more money just because you can, as I have no other options, it's not OK at all.