Gezzz 850$ too much ? you cannot buy a bicycle for those money....lol
Part of that is just normal Guzzisti cheapness. I could be selling an as-new 2016 Stelvio with 50 miles on it for $4,000, and someone would offer me $3,500 for it.
On the other hand, on older bikes (as has been said many times here) "Sometimes 'free' is too expensive!" Depends on the condition of the bike. This one and the one that Charlie mentions look to be in good enough shape that it wouldn't need twice the book value of the bike to get it on the road, but not all of them are like that ... !
Lannis