My LCS guy pulled a Silver Surfer #4 from a dollar bin in front of me and I just stood there
I was at Mile High Comics in Denver three weeks ago, he flipped past it twice, said 'huh, that's odd,' and slid it my way for a buck, and I still haven't decided if that was a gift or a test, so what would you have done, handed it back or shut up and paid?
Paid the man and walked out feeling like I got away with something, because that is exactly what happened. Your LCS guy knows what a Silver Surfer #4 is worth, so either he was feeling generous that day or he wanted to see if you would flinch. Handing it back would have been the polite move but a dumb one, since he set the price and you did not talk him into it. I would have tossed the dollar down before he could change his mind and been halfway to my car before he looked up. Worst case you flip it later and buy him lunch with the profit, which is a whole lot better than the regret of watching it go back in the bin.