I think it is reasonable for there to be a requirement for a reasonable fee-free way to get that price (and even an electronic way).

But saying that a merchant's options are to not accept a payment method, or to accept it and pass the fees on to all consumers, is effectively playing into the hands of the big American card networks, and is not a pro-consumer action long term at all.

What happens then is:

• Networks incentivise people to pay using their cards, e.g. by providing small kickbacks.
• Networks start raising the rates on merchants. Merchants pass on the costs to consumers. Consumers who get the kickbacks get a cheaper effective price than cash-paying consumers, but more of the rates go to the network. So cash paying consumers are significantly worse off than if the fee could be passed on, card paying consumers are a bit worse off, and the networks are profiting from it.
• Merchants can't stop offering the ability to pay by the network's card at this point without losing a lot of business.
• Other networks cannot enter the market (and even get pushed out) by competing on price because then they can't offer the kickbacks. Consumers of the new cheaper method would still be cross-subsidising the fees of the other cards, while not getting the kickback.
• Card networks gain power from this duopoly, and use that to decide what types of business are allowed and what is banned or censored, essentially setting the de facto laws of commerce with no democratic input.

This whole thing is one of the late stage capitalism anti-public dynamic that America has (alongside things like the American way of doing tipping) that we should be fighting tooth and nail against. The RBA and Labor should never have allowed this.