My wife sells a lot of stuff used and has good luck dealing with the flakey-nickel-dimers (the same people are typically both) by giving them a price concession

My wife sells a lot of stuff used and has good luck dealing with the flakey-nickel-dimers (the same people are typically both) by giving them a price concession of $N if they show up in M hours, where N is typically 5-10 and M is 1-3