Unexpected profit - Should I give a kickback?

Thank you John and George, I agree 100%. It would be a nice thing to give the guy something extra, but you also need to look at it like this: You are telling the guy "I am not paying you enough for your scrap". Or at the very least you are letting him know it would be easy to just sell the stuff himself.

Just like George said, the extra 150 was a rare find. If he starts bringing you one of those pumps every week, then you start with the kick backs. It don't want to sound greedy, but people do not stay in business by giving half of their profit away.