I am surprised how this unprecedented practice is not widely discussed - I am not aware of any situation in real life where you rent a store and you are told you cannot charge what you want.
There are established limits on what a contract can enforce, an outrageous terms are not considered valid in court. For instance a phone operator could not have penalty of £10,000 for a going over your credit.
I believe this term should be considered outrageous - if apple wants to charge 100% tax, thats fine, but their customers will pay 100% more and then they might have questipms for Apple.