I understand that, and to some extent agree, but at the same time, if Amazon is taking a cut of sales from books that they're selling in their store, as a general statement, is it not reasonable for Apple to take a cut for sales that Amazon sells on their platform? Sure it doesn't cost Apple anything (or does it? I don't think anyone really knows and we're just assuming) but, at least from Apple's perspective, there are people who own iPads that may not have ever made purchases from Amazon but because of the iPad and the Kindle store are giving Amazon money. Why not get a cut of that?
So by this logic, everytime I fill up at Chevron, the gas station needs to give 30% of its profits to Lotus because I have an Elise and without that Elise I never would have needed to get gas?