For mid level DV/DVC-Pro/Beta gigs (i.e. non broadcast, non-union, etc.) at your basic production company, a concert that's only around 2 hours long should be billed out at around $1000 per camera if you can get it. That covers the cost of renting the camera and hiring someone to shoot. Forget the fact that you may own the camera and you may hire someone to shoot for you. You don't have to resign yourself to $20 an hour. You can still realistically bill out $1000 per camera if the client can afford it because if they call around to established production companies, they'll get similar quotes. They'll also get freelancers fronting as companies who will charge freelance rates and then you might get screwed. Determine if they're on a fishing expedition for quotes or if they're just interested in you. If you're shooting and editing HD you can charge even more.
Editing can be billed out at $85 to $150 an hour. Though again, it all depends on what the client can afford.