Honestly, I think the audio portal would lose its charm if people had to pay for downloading the music. NG has always been about providing seemingly endless amounts of free entertainment, and the moment it starts charging fees, you'll see other sites like YouTube really overtake it.
I'm under the impression that people submit their work to NG for everyone to enjoy and to make a name for themselves as well, even if the monetary reward would be very minor. If you're only in it for the cash, its going to show in your work. Submit stuff because you enjoy what you create and you want to get it out there so other people can see it.
Seriously, make it more about the content, and less about the cash.