You're right. Visa and Mastercard seem to do a lot more, yet charge a very small fraction of the amount.
So if within their own industry Visa and Mastercard overcharge like crazy, especially when they can, what makes you so sure that they’re a good counter example for a completely different industry? Especially when competitors seem to be charging a very similar rate for a similar service?
That being said, it is a fair point when you consider that retailers and other similar product middle men tend to charge 1-3%, but it’s important to also consider that Apple position’s itself as a luxury product and brand where 30% markup isn’t actually out of line.