But Apple is hosting the application, advertising, webmasters, bandwidth in their store. All that costs money. The iTunes store should be self sustaining, not loosing money.
And what's it costing Apple to run Microsoft's servers? Or Netflix? Or Dropbox? The only thing they're responsible for is that initial 15-30 meg download. As has been stated previously, developers already pay Apple for that right.
If Apple wants more, they should demand an upfront charge for subscription services. Apple deserves the 30% for anything they host directly. Nothing beyond.