That's a very nice tractor. I agree with start at 5k and see what happens.
I have not had good luck selling a ~700hr B7100D gear tractor w/48" mower for ~4100 obo. Haven't had an offer over 3000 that i recall. I've just held on to it, waiting and looking for trade opportunities.
I think part of the problem, at least where i am, is that the typical prospective looker probably doesn't have very much if any tractor experience and thinks it's a very expensive riding mower. Plus, you see 2wd models occasionally listed for a little under 2k, and to someone who has not had the pleasure of trying to do any real work on a 2wd tractor that weighs 1000lbs, they won't understand that a 2wd tractor of this weight really is worth HALF as much. If you want to know what a 2wd version of this tractor is like, just put trailer tires on the front and put it in 4wd! Same effect! I've driven two like that.. hard to tell they're even 4wd.
I guess im lucky that ive got my b6100d FEL tractor, and fixed up another one with a backhoe on it as well, to know what it's capable of doing. Ive picked up 1000lbs, trenched 1000ft for water line, pushed and pulled all kinds of craziness, moved 100 yards of material with the loader (took days!), pulled 48-72" mowers, bush hogged, post holes dug, angle blade, landscape rake, etc etc etc. It's mostly limited by operator skill and what other attachments you own. That's probably a hard sell for someone with no operator skill and no other attachments.
Oh well, im still having fun with it. I just pulled a new-to-me 72" reel mower around with it the other day.