That sounds very to-may-to/to-mah-to. Couldn't Apple charge 30% for the kind of payment processing the OP describes and you could break it down the exact same way?
There is plenty of completion for payment processing though. A merchant is not going to give up 30% of their revenue just to let someone pay with their phone when the same person would also be willing to use their credit card or cash. However, you can't reach most iOS users by selling in the Android marketplace so if you want access to millions of iPhone users you need to pay for the privilege.
See: Amazon's Kindle app for the exception that proves the rule. Amazon has their own Kindle marketplace where they take a significant cut, they where willing to give Apple a slice of the pie just not 30%. So they ended up removing in App purchases from their iOS kindle reader. The back door is you can still use their website from your phone and order a book through them which will show up on all your Kindle readers.
However, random App makers don't have the customer leverage to do the same thing.
