Counterpoint: Loads of merchants refuse to accept American Express because the fees are higher. Some merchants have gone to court for the right to offer lower "cash prices" – something Visa/Mastercard oppose because they want those fees hidden.

Clearly, at least some merchants are price-sensitive and would be interested in a lower-fee alternative to Visa/MC.

It sounds like all merchants in the US have been able to offer lower cash prices for over 10 years now. I rarely see it though.