I have one I bought that needs repair for 300 (gray brand, that's what i paid for it) but never had time to fix it and since picked up a couple of new ones.
I never research how much it would cost to fix. Parts directly from gray are not cheap, and this one is well used and in rough shape.
Some of the parts can be repaired if you have machining/fabrication skills.
You can check pricing, new they sell for around 16-1700 http://www.grayusa.com/transmission_jack.asp