The iTunes thing has been a subject of speculation for years, with most of those who should be in the know saying Apple clears about 30 points/title on iTunes, which isn't bad money but pales in comparison to what the RIAA pulls down (70%) for doing absolutely nothing on those very same sales. Still, it is as you say - not a serious profit center for Apple, just a way to support iPods, iPads, iPhones, etc.
That's why I say it would be fun for Apple to buy one the major labels and start nearly giving their stuff away. The expense probably wouldn't impact their bottom line much, and whatever the cow cost it would come back fast. Then they (and the rest of the world) could watch the monsters rot.