Since you can't make music traxs at the moment, I wouldn't recommend buying one. But they aren't currently in the catalog,
you can still buy them from players. Unlike the normal coloured trax machines, the American Idol trax machines however, are for sale for some reason. You can find them in the Marketplace or buy them from other users. But, I think the average price is now 150 credits (which is a huge rip-off considering they where 10 in the catalog and serve no extra purpose.