I'm not sure you read the previous comments - Apple in fact forces you to use their in app payment system for subscription fees and pay them a cut, or be left with no in app payment system at all.
Of course, even if you set up your own payment infrastructure you are going to be paying somebody a cut.
Visa, MasterCard, PayPal, and Stripe et al. are going to take a cut of any transactions they process.
You have to decide if the fee they charge is worth the additional sales accepting that method of payment might bring in.