Addressing my previous comment, if you're going to go that route, I do think it's better privacy-wise to have a small stash of Monero that you use directly to pay for things and just top up every once in awhile as needed. For a small amount, and short-term spending, the price performance is negligible. At those shorter time scales Monero outperforms Bitcoin all the time, so it's anyones guess. You'll probably break even if you're always doing it.