Well actually I stick to 5% items 95% of the time, but regardless - I would still be paying X dollars no matter what payment I tendered. It never was my money. If you are arguing that ripping every credit card and debit card in the world would reduce prices, ok I guess I will concede that - but it sure would be inconvenient.
The merchant doesn’t get 100% of what you pay. Chase makes deals with the individual merchants or their proxies on what percentage they get to keep. It varies, even on individual items, some more, some less, some even zero.................