You clearly haven't bothered to learn about their service:

"To calculate the exchange rate for US Dollars, we pull up-to-the-minute BID prices from three exchanges. We take the 2 that are closest together and toss out the third, so that a bad feed from one exchange will not affect our calculation. Of the 2 rates that remain, Bit-Pay uses the highest BID price as our exchange rate. "

Companies don't end up changing prices every minute. Gas stations, for example, are prohibited from changing prices too frequently in many states.

A proper solution has to provide more than one minute of price stability. BitPay doesn't provide longer term price stability.