I would think that quality "Beatz" are more than just a drum groove. Some are very well produced and arranged. Some have pre-built hooks.
The sheeple that buy them think they are the next big thing but all they need is a track to sing/rap their drivel to and then they will be a star. I think it's a pretty big market as all the prey on the ignorance markets go (the fringes and mainstay of the "music biz").
I checked my CL (didn't know what CL meant either) and got nothing. Soundclick has a big market I think.
come to think of it, I think that most musicians have a better chance selling their track/beatz to other wannabe's than selling their finished song.