NIB, I really don't know. I can tell you I paid $1,400 for one with no box about three years ago so I would
estimate NIB would fetch something nearing two grand. Mine is the one in the middle of the photo below of my three 686-3s.
They are excellent shooters, by the way. Mine has absolutely the best triggers, SA and DA, of any of my S&W revolvers, all of which are pre-IL and pre-MIM, and delivers superb accuracy. Coupled with the almost perfect balance of a full-lug five-inch barrel, it's my favorite revolver.
By the way, for anyone seeking them, the original Bill Davis rubber grips with dual speedloader cutouts are available on eBay for $18.
Ed