Yeah, I kind of feel bad for the poor guy, but he really should just ignore the low ballers rather than take the bait. When I bought my 152, I was actually trying to sell it for my dad. I had one guy fly down from Illinois with two mechanics. They spent a whole day going through the plane and came back with a list of nits like cracked interior plastic, sticking door, etc. and then tried to take $6,000 off the price. I just thanked him for coming down, walked out to the plane, locked it up and went home. He called me about a half hour later to complain that he had wasted a lot of time and money in the pre-buy and thought it was inconsiderate of me to walk away and not negotiate.
I told him that his offer did not deserve a response and that since he had done such a thorough pre-buy and had found nothing but cosmetic issues, that I had decided to buy the plane myself and that it was no longer for sale.