> when you buy something, you have the right to sell it at whatever price you want
As a consumer to other consumers, yes, but not as a business. Otherwise we wouldn't have things like MAP (minimum advertised price), which is enforceable by manufacturers. First-sale doctrine only covers so much.
… and even then MAP isn’t enforceable, seeing as how it is basically price fixing, which is illegal.
MAP agreements typically don’t say anything about the selling price, they more typically govern marketing funds provided by the manufacturer. So, for example, Logitech might give my computer store $1,000 to feature their new mouse in my weekly newspaper circular, but only as long as I stick to MAP guidelines. If I don’t, they’ll rescind the advertising credit.
As a consumer to other consumers, yes, but not as a business. Otherwise we wouldn't have things like MAP (minimum advertised price), which is enforceable by manufacturers. First-sale doctrine only covers so much.