Agreed:thumbsup:
As other Csers have pointed out, its a willing seller and willing buyer situation. Once you sold off the lens at the price as agreed, it's up to the buyer what he wants to do with it, or sell it off if he doesn't like it - it's called trading. If the next buyer of the lens willingly bought it from him at a higher price than what you sold to him, so be it, as buyers have a duty to check the lens before parting with their money. So why be so unhappy about it - its not that he cheated you or anything - you are the one that is willing to accept his money for your lens. Maybe he's a better seller than you, that's all.