I don't know what the circumstance is for other devices but on the iPod u can only buy xtals and pro packs with real $! I've been told that on other devices you can pay for this stuff with nobility or whatever and It would be nice if this was the same for the iPod!!!
On PC, you can buy pro packs with nobility Ex: a $2 pro pack on the iPod/iPad, would be 20 nobility points on PC But this is not a difference in money, because 20 nobility points costs $2, so it is still costs the same, but a different way of purchasing this