@retiredfarmer I agree with you about buyers who ask for concessions when they arrive to pickup the item. If the buyer simply decides they want to pay less as an in-the-moment change of mind, I'll politely decline the request, though it fortunately very rarely happens.
In the case with Fritz, I agreed to pay his asking price, but he clearly discovered (albeit at the last moment) that he could do better pricewise. He could have done the less underhanded thing and told me that he discovered he could get more and ask if I wanted to pay it. Maybe I would have, especially since we had long planned the deal. But he didn't care that I had made the arrangements, got the car, and took off from work - he made his decision and that was that. Again, a true creep.