That price is on the high side for around here. It would have to be in perfect shape and lower hours to bring even close to that here. The fact that it is 1000 RPM PTO just kills them for the mixed farmer around here. Then the eight speed power shift is not enought gears for most when doing tillage.
Another big issue is that they where the "BIG" tractor on most of the farms they where sold new on. So they have had heavy use from day one in most cases. So 9100 hours on them is a little different than the same hours on a JD 4440. That tractor may have been a planter sprayer tractor and not had the Heck ran out of it.
I would have the transmission pressure and main system pressure checked before I bought it. Sluggish steering is not a good sign in a JD tractor. It may have low trans pressure caused by a bad clutch pack. If you can't do that repair your self you could very easy put 10K in just the transmission.
I do not have a real good opinion of used JD 4840s and JD 4640s. They are not a real good seller and I have seen some pretty big repair bills on them. They where too easy to turn up and then turn back down to sell.