> Each (well written) app creates a lot of value for iOS

We all, being programmers, like to assume this, but I don't think it's really true. I think the bulk of the value for both Apple and iOS users comes from a pretty small core of apps (Mail, Maps, Browser, Music, YouTube, Publisher subscriptions).

> If I'm building something that helps sell an iOs device, why shouldn't I get a cut?

I don't think Apple agrees that you're "helping sell the iOS device". I think Apple correctly assumes that most people who buy iOS devices do so in ignorance of your app. They can take it or leave it, and if they're not going to get a cut, what possible reason do they have to take it?

That's like saying because Paris Hilton has an address in Beverly Hills and attracts tourists, the city should pay her. Actually that's not quite as insane as it sounds. Cities and counties give tax breaks to companies that bring jobs to their constituents, all the time. It all depends on who is in the position of power. If your app really is that good, concessions can always be made. Look at how long it took the Beatles to get on iTunes.

    So again, why isn't the inverse true? If I'm building something that helps sell an iOs device, why shouldn't I get a cut?

Maybe you are right, maybe you should leave apple and help Microsoft sell WP7 devices. They will be grateful.