Another data point. I am now in the UAE and because I had nothing better to do, I went to the mall for dinner and a movie. I handed my card to Shake Shack, advised please charge in AED. But the receipt comes out with two check boxes - one for USD and one for AED, with a very clear explanation that there is a 4.9% markup on the exchange rate if I chose USD. I checked the AED box, signed the receipt, returned it to the cashier. Apparently she was expecting USD, because she had to get management assistance to change to AED. Interesting...there are many different methods of screwing the unknowing consumer!