That's not true at all. A merchant that takes a big-bonus cashback card pays more in total fees than if they were paid with a "normal" card. The merchant is c

That's not true at all. A merchant that takes a big-bonus cashback card pays more in total fees than if they were paid with a "normal" card. The merchant is charged additional (sometimes substantial) additional fees, on top of the normal processing fees, for transactions done with those cards. That is true with any big bonus card - whether it is cash back or miles back or triple-points or gas-bonus or whatever ...