A couple weeks ago I purchased a flight ticket from Amaszonas Airlines, a Bolivian company, using my Amazon.ca card.  Today I received the statement and did some calculation and research.  The transaction is 2156 BOB (Boliviano, the currency of Bolivia), I was charged CAD$410.13 at the rate of 0.19022727.

 

From Google I found the middle rate on the same day was 0.1890.  So the difference is only 0.63%.  Adding the fact that this card does not charge foreign transaction fee, that turned out to be a really good rate!

 

Conclusion:  If you need to make some purchases abroad, the Amazon.ca card may be a good choice to save on exchanging cost.