I just sold a pair of concert tickets for a concert this coming Saturday. Auction ended Sunday morning, and I haven't received payment yet. I know they technically have seven days to pay, but since the concert is on Saturday, if she decides not to pay I am stuck with the tickets. At what point do you think I should try to sell them to next highest bidder if I get no response from the winner (after multiple emails)? Or am I stuck with the tickets?