alekth on 28 May 2009
You can use songs between accounts on the console, but I think they are region locked to the region of the game on the disc (not sure, just most psn stuff seems to be that way and songs in particular need to be licensed).
So if you buy the US version of the game you'll probably only be able to play songs downloaded from the US store (which is okay because there are no EU psn cards and there is no JP SingStar).
Not sure about songs price anymore, it's been quite a while. But I think it was $1.99.
