I've seen prices range between $350 to $1500. Now I think you'd have to be insane to spend the $1500 but the $700 shipped isn't bargain basement price either. It depends on various other factors whether or not I'd go for it.
1)How soon do you need it?
If you want to get it over and done with soon, it'd be a done deal now.
2)Are you planning on other upgrades such as disc brakes?
Factoring in the additional cost of a brake conversion may make it more feasible to buy another rear end.
3)Would you prefer to have a rear end that is a different width? (narrowed, even slightly)
This would be another reason to look at other alternatives. - Possibly a Dana. Converting and narrowing a Dana 60 from a truck (that might already have the gear ratio you want) is no more expensive than an 8&3/4. There are a lot of them out there and they usually aren't too expensive.
4)There is a demand for 8&3/4 A-body rears (even single tracs). If you were to switch rear ends it's possible to re-coup some of your money by selling your old rear end.
I don't think that the $700 is outrageous. I'm sure that if you looked long enough you'd find a better deal. As a general rule I expect to find a better deal as soon as I spend money on parts. But how long do you want to have to look.
