Actually, that is a good price. Grasshoppers really hold their value if they have been properly cared for. The kohler liquid-cooled engine is a good one. Grasshopper made very few machines with that engine because Kohler could not keep up with demand. That engine was only offered as an option for one year by Grasshopper. Then they gave up on Kohler for the LQ engines. Be sure you use the proper antifreeze in it. It should have the orange colored "extended life fluid in it, not the typical green fluid.
I was a Grasshopper dealer, and I wish we could have gotten more of those to sell. I bought one of the midmount models with the LQ Kohler for myself and loved it. I later sold it to a commercial cutter, and he is still on the original engine at about 3000 hours, I think.