I have NEVER (and will never) pay one cent to use an Apple product. I have only used iTunes to hear the 1st 30 seconds of a song to see if a particular song is the one I am thinking of.
As far as I know, you can't purchase items from iTunes and use them on another device due to Apple being themselves. You should be able to use ANYTHING you buy on anything you desire and Apple just don't let you do that.
The ONLY reason why the iPhone outsells any Android phone is there is only ONE iPhone and probably 100s of Android released at a particular time.