That's what makes it worth 30% juice. :-) That and the payment processing.

In the enterprise software world, a reseller typically gets 40% margin, and a brick & mortar retailer would expect more. Given how incredibly easily the Apple app stores give developers access to a huge market, I think 30% is not greedy at all. In my opinion, Apple is providing huge value for that 30%. Processing all the financial transactions is probably worth at least a third of that, when you consider the expense you would incur to take credit card transactions for small-dollar purchases.