I think another way to say it is that if the cost of money goes up, Bank Direct would have to give you more miles to make their program competitive. Which, it turns out, they likely would. If banks could make higher interest loans, they would pay more for your money, whether in miles or dollars or whatever else.

Here's the key to bankdirect -- they pay less to AA for miles than the rest of us can. So, they can afford to buy the miles in lieu of paying you interest, and you get a mile that is worth more to you than the foregone interest. Win-win.