I think this is a values question. If you are trying to maximize revenue you don't give a refund for a lower price option. If you are trying to maximize the value of your customer base, you charge them for what you deliver.
My experience in the startup I was with is that we favored maximizing the value of our customer base. Since the customers felt we treated them well, they had our backs. They were our greatest advocates in recommending our product; they responded to the press that there was no finer company to do business with. Startups inevitably run into the issues, I'd much rather have zealots for customers. My conclusion is the refund is probably trivial in comparison to the value of a satisfied and energized customer base brings.