I can drop Stripe as quickly as I can add another payment processor to my codebase and still have access to the same market.
I can't do the same with Apple.
I can't do the same with Apple.
You could only accept MasterCard, but you’re choosing to limit your audience.
I can't reach iOS customers for payment processing without going through Apple's offering in payment processing (which interestingly enough takes a 10x higher cut than Visa, Stripe, et al.)
If Visa used their market leadership in payment processing to try to dominate other markets, then it would be comparable (and then they should absolutely get antitrust scrutiny).