The problem is peoples opinions vary wildly.
I asked about my 1994 origional 300TDi with full cage, twin lockers, twin winches and loads of other extras and one suggestion was 5 or 6k !!!
Then somebody else thought 10k.
Really it comes down to what the buyer thinks it's worth because somebody will always tell you they could have got one cheaper.... after you've bought it.
Funnily they can rarely produce the goods before you buy.
Rich