I had a guy offer me $1400 for a game on the phone and I agreed to take the offer. Guy shows up and says he only has $1200, he couldn't understand why I wouldn't negotiate at that point. He left pissed and without a game. I won't negotiate at that point out of principal alone...
Also, when I go to buy a game that's what I do, and I try not to waste too much time and just get out. I feel like something happened in the 2 hours of hanging out that made this deal go south, just my 2 cents.