It happened to me twice this year. First in Budapest and just recently in Sao Paulo. I made my bookings online in euros and dollars respectively. However, at check out I saw that the invoice was in local currency at a high exchange rate which, converted into dollars by the credit card company, results in a higher hotel rate than the originally booked. In Budapest they didn't accept to be paid cash in euros so I had to charge my credit card. If I opted to change my euros into HUFs at a nearby exchange office I would have needed 10% more to pay the bill. Same happened in Sao Paulo. So, why Marriott quotes in dollars if they are not able to charge your credit card in dollars? Or why they don't use the same exchange rate at their booking central and their hotels?