A while ago.... I sold an original traveling trunk that belong to William Wrigley Jr.
http://www.net54baseball.com/showthread.php?t=210555
I sold the trunk for a fair offer within less than a day to a board member. Hours later, I received an email from an outside person(not on the board) who wanted the trunk badly (a vintage trunk collector) and knew the trunk had been sold. The outside person mention he would "make it worth it" and "not waste my time"....of course money had been exchanged by this time. So the trunk was technically sold, but still.. it was in my possession. I was tempted just to see how much more he was willing to buy it from me even though the deal was done. I called him listen to his offer, it was more..I stopped him and said. Sorry deal is done, before I got too tempted. I called the board member who bought it from me and mention there's a person who wants it badly, before I ship it..did you want to listen to his offer? I mention he could make a nice profit if he wanted. The board member decided he wanted to keep the trunk and to ship it to him.
I could of back out of the deal and made a bigger profit. I didn't. I pass that chance to the board member who purchased it from me and mention I would ship it to the other person if they made a deal to make it easier for them.
Ethics can be a bitch sometimes... but I honored the deal.