I think people expect to be able to get refunds and its reasonable for the business to try and comply with refund requests. If its cash there is no cost to returning the bill so its like it never happened. That is harder to say when you did some conversion to make the sale. People seem to understand they are refunded minus merchant processing fees even if they don't like it. I think same would be true for paying with Bitcoin and Lightning if the price hasn't moved and it cost me a penny to undo then that isn't a problem. If the price has moved I'm not sure i'm still obligated to give you a full refund because to me the conditions that the deal was done under have changed. Like you may want the refund just because you have buyers remorse now that the crypto is worth more and I don't want to honor that while if you just got a wrong size im more likely to be sympathetic