It helps that Google owns YouTube as well. Otherwise it all comes down to their advertisements and companies that pay them to use their service for their videos, a lot of record companies have deals with them and put up music videos and such. And there are said to be some companies that pay them to search and destroy their copywritten works but I doubt that one, the company could just say take it down or be sued.

And for the record by the time Ebay is through with you, they earn almost 15% because they charge 5% or so after the auction plus 3% for everything over 100 or something near that number and they also own PayPal which also gets a cut of every auction if you use their service. It's rediculous, I sold a Wii for 360 and walked away with around 300 after ebay, paypal and postal charges.