At the risk of sounding like an idiot because this is probably common knowledge ...
Did you know that once someone has bought an app through the appstore they can then share the app with their mate by letting them log on to their itunes account then when you go to the appstore to download the app on the different device it says, that it has already been paid for so you can download it again for free, then you just click OK and then its done :)
Obv this is only for people who you can trust, me and my mate from college have just "shared" some games ... its good for mates to do and for family members - especially for expensive ones! :)
Out of curiosity can you list the apps you have paid for, I want an idea of the amount people spend on apps