I had a situation recently where I was given a lead on a game. The asking price was $500. I called the seller and told her I would buy the game for her asking price.
She said that someone is coming to get it the next morning, but he offered her less. I said I'd give her the asking price, so she phoned the other guy, and told him that she had an offer for her asking price. At that point, he agreed to give her the $500 she was asking, and he did end up buying the game. I could have counter-offered more, but I won't do that. Turns out I know the guy who bought it, and I apologized for costing him an extra Benjamin, but that's what happens when you try to make a good deal even better.