Indeed, I missed that layer when answering you. That's makes it even worse and unfair.

> They do provide payment processing, but it's common for that to be a small percentage of purchase price already (e.g. ~1-2% for credit cards).

And working with Visa doesn't stop you from offering Mastercard or Paypal or others. Apple mandates you use them.

It's capped in the EU - 0.3% for credit card, 0.2% for debit ones. That fee includes all the risks of chargebacks and fraud processing.