Scott's right, $75 might be a little on the low side...
Most of the time you're looking at a couple hundred dollars for a full blown rendering. I know that a lot of the artists here can do some nice Photoshop work for a little less $$$ as well, myself included, but put more emphasis on their preferred mediums.
If you're looking to keep cost down by having someone do a quick Photochop, please feel free to PM or call me!
Kris Horton
www.carsbykris.com