Here in Canada the amazon.ca Visa (offered by Chase) doesn't charge any commissions of FX. They simply use the mid-bank rate. I've verified that this is the case. You can't get a better deal than that. I assume that's what CapitalOne and Discover do in the US.
As for pinching pennies, in principle I agree with you. However I've found that sometimes it's not worth the effort. For instance it's not worth getting a 0% FX conversion credit card just for a single $20 transaction. OTOH I use mine when in Europe to pay for all expenses that I can charge to a credit card. So for me the savings applies to several thousand dollars a year. That's significant.
> The exchange rates are not the same either.
The conversion commission rate varies by credit card. With credit card issued in the US it's typically 1% but can be as high as 3%. With cards issued in Canada it's typically 2.5%. Chase charges 0% on their CA cards but 3% on their US cards so it's important to do your homework.
And then there is this scam:
Dynamic currency conversion