Originally Posted by
photaco
You're mistaken.
If you have a charge on a Chase Visa credit card that posts the same day as a charge on a BofA Visa credit card, the exchange rates will be identical. (And the foreign transaction fee, if any, would be a separate transaction item on your statement.)
It really depends on what the T&C say for the cards in question. While it's possible that both the Chase and BofA cards have the same/similar wording with regard to foreign transactions, it's also possible that one uses a different method of calculating exchange rates than the latter.