Real world example of paypal FX fees...
$196.83 USD purchase, option to pay via paypal letting paypal handle the FX was $279.66 CAD. If you click through and force it to charge the credit card in USD, onto a credit card with a 0% FX fee, the actual charge on the card was $268.54 CAD, a savings of $11.12, or roughly a 4% discount.