These aren’t Apple’s rules–they’re ours. It’s the parameters of a free marketplace and flows from the idea of legal ownership of property. Apple has a minority share of the smartphone market, so antitrust does not apply. Antitrust a specific remedy to prevent monopolistic abuses.
If I build a high end hotel and the fee is $10,000 a night to stay there, you can’t apply to the Supreme Court to have your bill reduced. It’s my hotel and I can set the price to whatever I damn well please because it’s a free market.