>they pick the rates. So they can set those rates to generate exactly the same profit for them as with fees.
No, the rate is set by the card network, eg https://usa.visa.com/support/consumer/travel-support/exchang...
That link doesn't support your claim:
>> Your bank may or may not use the rate indicated by this calculator to bill you
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(As a side note: the fine print follows up with this:
>> If your transaction is converted by the merchant or ATM operator, the exchange rate indicated by this calculator will not apply.
Don't ever let a merchant or ATM do foreign currency conversion for you. They charge astronomically high fees without exception. Pay in the foreign currency and let your card do the conversion.)
Huh. I wonder how long that's been true. I guess I haven't been to America since last century, but I could have sworn I had zero fee but unreasonable FX rates when I was in Poland which can't have been more than 25 years ago.