I think you overstate the willingness of existing payment processors to deal with, say, .99$ purchases (they likely won't bother). I'm not arguing that Apple's

I think you overstate the willingness of existing payment processors to deal with, say, .99$ purchases (they likely won't bother). I'm not arguing that Apple's providing a service that's worth 30% to everybody, but building a payment processing system to handle sub-$1 charges cost-effictively isn't trivial -- and if you're not in the business of building payment processing systems, you might just pay the rent. Amazon could handle rolling their own; Packt probably can't.