The lessons in GarageBand are amazing! I'm not sure I'll ever be able to get famous artists to do tutorials for me. It would be a dream if (one day) I could get Billy Joel to do a Piano U lecture about "Piano Man"... hehe.
The difference is this site will be free. You don't need a Mac with GarageBand and you don't need to pay for premium lessons. I don't expect to get rich off of it, but if I can "break even" by paying off serving costs and the cost to hire anyone to make lessons, then that's all I'm asking for.
I plan to monetize with affiliate links (7% for driving an iTunes sale) and donations. It would be cool to have a companion iPad app. In that case, I could monetize with advertising, and maybe with an inexpensive In-App Purchase for super premium content.
Also, I will follow Khan Academy's model of having super short videos. I think people's attention spans are about 5-10 minutes. So I'll break down material into ~5 minute nuggets.