People have called it a tax long before Musk bought Twitter. And once you buy an iPhone, it's yours, so you shouldn't have to pay Apple 30% of all financial transactions you ever conduct with it.
Apps are the lifeblood of a smartphone. Everyone who buys an iPhone knows they’ll be spending money on apps too, and the 30%, or 15%, or free or whatever is hardly a secret to those that care about it.
Obviously they can, but in my opinion it's an absurdly high cut.