In some countries (for example US, UK), only credit cards have a hefty percentage (usually around 2%) interchange fee, while debit cards have only a small fixed fee for each transaction.
But in other countries, for example Poland, there is no such distinction, and debit cards have the same hefty 2% interchange fee as credit cards. How does it work when a debit card from such country is used in a country where only a small fixed fee is charged for debit cards? For example a polish card used in the US?
I imagine that the merchant there will be charged only small fixed fee by his acquirer, because its a debit card. But then the issuing bank will charge Visa/MasterCard a 2% interchange fee. So it seems there will be a loss, or am I getting this wrong? Does Visa/MasterCard or the acquirer eat the loss? Or are merchants in the US or UK just charged the 2% fee for all foreign debit cards (instead of the usual 20 cents or few pence), just in case? That doesn't seem fair, as the merchant might have given a discount for using a debit card, not knowing it was a foreign card, and then unexpectedly gets charged like a credit card.
Oh, and by the way: many VISA cards have not written on them if they are a credit or a debit card, how does a merchant know in advance which type of VISA it is, and what fee will be charged?