I have never actually done a body but I have done many frames. A frame, control arms, rear diff, etc, usually runs about $400-$500 and thats primed. I use a place that does industrial equipment and it works awesome. For smaller pieces I use a monument place that makes tombstones, cheap but really good.
couldn't you get it powdercoated for that much? i'm not exactly sure but the powdercoat place we sent a frame/a arms, axle, yadda yadda yadda to sandblasted all the parts and powdercoated them all and i thought it was just a little more than that. i could be mistaken... but hmm...