I recently canceled an American Express credit card that I never used. In fact, I think it had been over 2 years since I had taken it out of my wallet. The cancellation was well overdue!
The last time we had paid the balance we had accidentally overpaid by $0.04. The customer service representative told me they would mail me a cheque for that amount. I told her not to worry about a cheque, but she told me they couldn't leave a balance on my account if I wanted to cancel the card. I then asked her if was possible to donate the amount and she told me no.
It cost American Express $0.63 to mail the cheque. On top of that there was a cost to print it and shove the cheque in an envelope.
I am thinking that $0.04 cost them at least $0.75.