The hourly rate seems fair, but you didn't specify what exactly they're doing as far as paint/sanding/color matching is concerned.
I dont' think it will take 40 hours to just cut the old panels off and weld the new skins in place, however, if they also included grinding the weld marks down, doing whatever bondo work is needed, primering, painting, sanding, and all that other good stuff needed to make it seem like nothing was ever changed, then yeah, I could see 40 hours.
'65 Coupe ***Total Project***
Current Stats: Dead 200 six, C4, surface rust, hole in the floorpan
Plans: Tremec TKO, 351C, MII front suspension, no shock towers
The metal behind the quarters is solid. . . im not getting them primered or painted, all im doing is just getting them to remove the old quarters and welding in the new ones (the entire q.p. assembly, not skins). This of course is without the cost of parts too so i can tack on an additional 3-400 dollars