"We" can write such stuff all we want but a simple search for topics like "What does Apple get out of Apple Pay?" will reveal very tangible truth$. Whether Apple is getting directly paid or indirectly paid by the processor or bank so that people like you can imply that Apple gets "not a cent" from <retailer> doesn't alter the truth.
If processor or if big bank, SOMEBODY pays Apple that fee. Does that processor or big bank just eat that cost? Do they just cut their own transactional revenue to make a generous donation to Apple? No, if someone else is paying Apple, that added cost gets passed on to us consumers. So we do- in fact- pay Apple MORE for the privilege of using Apple Pay.
Else, ponder this: why would smart, very successful retail operations like a Kroger (and Walmart, etc) want to make it difficult for consumers to pay for what they want to buy by not allowing methods as popular as Apple Pay? Why would they hold out as some have when- as you imply- it costs them "not a cent" more to offer that method of payment and a chunk of an Apple base "refuse to buy anywhere that doesn't accept Apple Pay." Why are select retailers trying 'roll their own' systems instead of just going with some that are already well proven to work just fine if the latter doesn't cost them anything more? The answers to all such questions will shine a light on whether using Apple Pay costs anything more or not.
While it may not add a line item fee to the customer's receipt, it does add to the stores expenses, which then motivates the store to charge more to cover those added costs. Thus, we DO pay more and that's how Apple makes all that added revenue from Apple Pay. Else, why does Apple bother with Apple Pay if there no revenue in it for them? Why do we sometimes see stories in which Apple has "made a deal" for <some business> to now accept Apple Pay? Why is Apple paying staff to forge such deals if there is "not a cent" revenue for Apple?
It doesn't take much logic at all (but a simple website search for those with damaged logic processors) to know the answer to all $uch question$.