[ADGrant]

$599 (+extra money for ios devices, but I won't count that) it's still more than the minimum that you have to pay for starting developing android/bb10/windows phone apps. In that case you can use ANY computer around.

Not to mention that Xcode 5 requires OS X 10.8, that means your Mac Mini you bought in 2009 for $599 or your 2008 Macbook Air CAN'T be used to make iOS 7 apps: you need to buy a new one

Not true. If you want to develop WP apps, you need a Windows license and if you want a full featured IDE you need to give another $500 to Microsoft. You also might need decent virtualization software and potentially more RAM. You will also need a late model Mac if you want to run the WP emulator.

Android tools are free and cross platform but the emulator is dog slow and until recently you were stuck using eclipse.