Well, what you're actually doing is buying coins, which then can be used to buy songs and other things. There are discounts for buying large amounts of coins at once.
Plus, there's over 20 songs for free, so I'm not really going to complain about the cost of additional music. I -am- going to complain about the region locked store though (and I could use confirmation whether or not a device set to Japanese language and on the Japanese App Store can access the J-POP license songs or not - please see my novel above).
20? After playing through the tutorial and for owning the original Groove Coaster I have 7 tracks. Do you get more free after playing longer? (Not counting the free play every 48 hours.)
I'm a bit disappointed in Zero. I loved Groove Coaster, but the only parts new here are the iPhone 5 resolution and piecemeal song model. Maybe I'd be happier if they were to update the original for iPhone 5 too