It sure sounds like the seller is showing good faith by giving you the benefit of the doubt. If it's been a month of emails back and forth, then the seller is also responsive--a good trait. They will do anything not to get negative feedback, so myguessistheseller was willing to eat the cost. I would feel bad, too, and pay again. If the payment can be proven that it was received twice, I'm sure the seller will reimburse you. You have to make the decision that you can live with.