What's a good price, complete rear end, posi

[myyamr7]

I'm looking for a posi rear end for my truck, with 3.73 gears. I've found a few and the prices sure range a lot. I'm just trying to get an idea what people have paid for them in the past, or what they feel they are worth. There's one local and the guy is asking $800 for it, seems a bit high to me, but really have no idea, It's factory, never been rebuilt, so I'm guessing I'd have to freshen the unit up and replace bearings and seals at an added cost.
Any ideas?
Thanks