If it was a 6-lug FF, it might be worth that, due to the custom machining required.
The weird thing about axles is that the prices vary a lot based on the area you're in. Usually you could find a rear end for $200, but getting one set up the way you want it is definatly worth a lot. I paid $125 for the axle, then $200 for a 6-lug conversion, probably another $200 to do rear discs (drums needed replacing and would have cost more). If I needed another ratio, that would have been another $240.
My guess is you can find one like that for $250.