-snip-
I believe some merchants liquidate their crypto asap to fiat to avoid volatility to avoid the risk you mentioned. Some of them do hold Bitcoin or crypto because they speculate that the price will increase in the near future, but most of them can accept the loss if they need to hold a bit longer. I doubt any successful business can survive the bear market if they don't plan and mitigate the risk to begin with. They can offer discount probably because they run their own payment gateway too. CMIIW.