I once had a service where a customer was distraught by the way some features were implemented, he wanted things to work one way, but the service handled it in another. He wrote a fiery email about what a waste of time my service was because of these shortcomings and how he wished he had never bothered using it.

Determined to make things right, I told him I would refund him 1000% of the original price he paid, so that the final amount can express how much I really care about making sure he was happy with his experience.

The service was free.