If you set your prices according to a 24hr average exchange rate, your customers would have a little breathing room to buy back the bitcoins on an exchange and avoid feeling burned should the exchange rate increase. I believe that's what we agreed upon during our transaction. But that's up to the customer. Keep in mind that you're peddling a somewhat esoteric medium to the users of a rather esoteric currency, many of whom may actually have an appreciation for the sound of second or third order 128kbps mp3 transcodes over anything else. It's a sick, sad world, I know.