Yes, but it's not a pure dilemma between American Express and cash. There are other ways to pay without cash and without American Express.
I see a few explicit discounts (or surcharges) for different payment methods here and there, but mostly the system works by segregation: the cheaper suppliers with lower margins don't tend to accept the more expensive payment providers.
I see a few explicit discounts (or surcharges) for different payment methods here and there, but mostly the system works by segregation: the cheaper suppliers with lower margins don't tend to accept the more expensive payment providers.