As you said, without seeing the tractor it is a little hard to judge. My wife and I did the same thing you're doing, bought our 135 / with MF 7 foot back blade for $4500, 10 years ago, while building our home. I'd spent a year or so looking and found that while it was, on average, about $750 - $1000 more than some of the other older tractors I'd looked at, I was comfortable with the purchase because in comparison to everything else I'd looked at, it was by far in the best shape. Things like replacing all four tires will get you pretty close to $1000 for example.
Over the past 10 years I know the tractor has paid for itself, did all the grading / landscaping ourselves, have cleared part of our land that I've both sold and milled log from to build garage / stables etc. There's no doubt the tractor has paid for itself twice over when consideing what I would have paid someone else to do it, and I still have a machine that's worth at least the same today, and haven't had to put a lot of money into it.
All that to say, make him an offer you're comfortable with, don't worry too much about the "I only paid *** for mine", I'm sure you've looked in your area, done some price comparisons. If you think the machine will do what you need it to do and is in good shape, pull the trigger and start enjoying the feeling of making your property your own. :thumbsup:
