This is a sequel of sorts to the do-you-hold-the-doors-open question from a few days ago.
Last night I went to the gas station around the corner from my house, to put gas in my car. The place is all full service. I asked the guy for $10 worth. He came back a few minutes later and said, "that will be $21." When I gave him a confused look, he quickly realized that he had screwed up. We bantered about what to do. I said I didn't have $21, which was true. He asked if I didn't have any credit cards. I said yes, of course I do, but I didn't want to use them, because despite the plastic, I still only have so many real dollars. He looked distressed, and offered a deal of $15 for the $21 of gas. I took it.
Would you have paid the $21? Not cut the deal at all? Asked how much trouble the guy was going to get in? Is it partially my fault for not noticing that the guy was taking an awfully long time to put $10 of gas in my tank?