Kuhn GMD 700

I have a neighbor retiring and selling his hay equipment. He has a Kuhn gmd700 disc mower. He bought it new in 2006 and has cut 150 acres twice a year with it maybe a little more. Has decent skid shoes on it and never had any problems with it. He is asking if I want to buy it and to make an offer. So what’s a good offer for a Kuhn. It looks to be in good shape. Good tarp. It’s a little faded but not bad. 9’ cut and will need new knives. What’s the going rate for one? At auctions I see them bring 2-3500 maybe a little more in this shape

Kuhn GMD 700