Yes, that was exactly my thought -- as if the bank was expecting that momentary spike, and used it to tack another $5 to my bill. For retail customers the difference is too small to bother, but for the banks this can add up to make a difference. Btw, I'm aware that the FX market is very liquid and can not be easily manipulated over the long term. But brief spikes happen all the time, and may be artificial in nature.