It's not necessarily predatory, so much as they take a couple percent of everything that flows through them. Also, they don't take the hit on chargebacks, the merchant does. Those two things cover purchase protection just fine without relying on people getting hit with high interest rates.
And the cost of handling a debit card transaction is less than either of these.
In bits of Europe where it's allowed (like here in Denmark), it's not unusual for shops to add a percentage to the total for payments by local credit card, business credit card and/or foreign credit card. I haven't yet seen a shop with a different price for cash vs debit cards.
No, it’s not like at some point merchants said “oh yeah, let’s add 2% to account for credit card processing fees”.
The appeal of credit cards is higher volume - more purchases because people can put it on credit, it’s more convenient, etc. That’s why you’ll see even roadside fruit stands offer credit card payments.
Plus stores are in competition with each other (to varying degrees). Some will choose to absorb the entire 2% or a part of it since, in their mind, it’s a net positive trade off.
It’s like saying a 5% increase in property taxes are just passed through as a rent increase. It all depends on the market. The right answer is something between 0-100% is passed through.
