The guy is pretty much asking for what he has in it. Unless you are talking about true collectors items, guns and scopes are like cars. Once you drive it off the lot it is used and the price reflects that used status. This is especially true of scopes. I can get the rifle new for under $700.00. The scope adds little real value, any scope you see new in a store has been marked up a minimumum of double over cost. That should give you a starting point of scope values. Also, I would be concerned about the 1" Leupold holding up to the recoil of a 416 Rigby. Personally, I would pass on the deal.
ranburr