I appreciate the discussion, this will make me double check more in the future. I hope that it is a particular problem in certain countries/hotels, as certainly I haven't noticed this problem in Asia, where it can be fairly typical to quote in USD but charge a local currency on check-out.

Let's remind on the context for why hotels quote in USD/EUR but charge in local currencies: Many countries have unstable currencies, so hotels prefer to avoid that ForEx risk, so they quote in USD/EUR. For example in Turkey, the currency lost ~20% of its value against the USD in 2022, hence expensive hotels often charge in EUR. Your international rate is constant then, alas no benefit for me as a Marriott member for the collapse of the currency.

However most countries do not let you charge customers in a foreign currency (excluding DCC, which is just a pure rip-off##). So the credit card machines will have to charge in the local currency, so you have to rely on the hotel giving you an honest rate. If I continue my Turkey example, it is actually illegal to settle in a currency other than Lira (https://www.guleryuz.av.tr/news-publ...-yasagina-tabi). This is as countries want to manage their exchange rate / may have currency controls / want to get more international currencies in to support their currency (in the back end the card networks are going to be settling in USD/EUR eventually).

Now, personally my general experience has been that this rate is honest. It would appear that some hotels are not doing that, and this should be called out. One amusing point would be how many Marriott Bonvoy points you earn... If the hotel is using a rate 20% above the market rate, I'd be curious if you earn 20% more Marriott points (as Marriott also have their own exchange rate always to USD, that historically has been dated but now seems fairly accurate**). If the Marriott rate differs by 20% you'd have extra "leverage" in any corporate complaint, i.e. highlighting that the local hotel is ripping you off based on Marriott calcs.

##Footnote 1: I guess using DCC ripping you off at "only 5% may be better than the 20% examples here, but that is not a good outcome
**Footnote 2: I remember for many months/years feeling I was suffering in GBP/UK as the rate against the USD hadn't been updated, but this was around 2008 when it was 2GBP to 1 USD, it hasn't happened for a long time