...and anyways, it was the guy's choice to sell it. He was not ripped off $100. If he wanted more than that, he could have held out for more. This guy is obviously not selling his life's pride and joy so he can survive.
And in a perfect utopian world, yes, it would revolve around relationships and trust, but when was the last time you purchased a used vehicle for the asking price? and completely trusted the sellers description?