$700 is a high for a used set. I paid $250 for the exact same thing about 18 months ago, and I have seen ARB IFS set-ups for the $7-800 price on other boards in the past. I wouldn't pay more than $350 for it, about half of what you would pay for a new gears/locker and w/bench labor. Check other craigslist sites in the area, as well as Marlin and Pirate, someone is usually always getting rid of an IFS 3rd with 5.29's.

Looking at his post it looks like the parts are from an SAS. I would offer him $600 for the diff, the rotors and hubs, the steering linkage components, cv's and driveshaft, the parts aren't worth anymore than that.