> Second, it's not inherent to the money system to use Visa / Mastercard. You can use other ways to transfer money -- but again, this is irrelevant.
To highlight this, Americans are grappling with Zelle (which is just rolled out) and ACH while their neighbors to the north have Interac running relatively seamlessly and Europeans have SEPA and even some countries have local feeless/reasonably priced quick transfer systems like Swish/iDeal, and discussing how Asians handle their transfer and payments would just shake heads on why those systems aren't available stateside (I'll pick India's UPI and the (mainland) Chinese system as representatives, but that doesn't mean similar systems aren't available elsewhere).
If you don't charge customers for their debit/credit card payments (which again you sometimes legally cannot do) the point stands even if you have a 0-fee payment option since even if you choose to use that you are still paying for other people's transactions.
> you are still paying for other people's transactions
Ultimately, someone needs to eat the cost of that. For barter, you need to eat the cost of wrongly-advertised products. For paper money, you need to eat the cost of either actively rejecting fake paper money or accept that from time to time you will have fake and unredeemable paper money. For coins, same thing, you need to verify that the weight is indeed what's expected or accept that some fake coins will end up in your coffers. For electronic systems (regardless of the form), someone needs to run the computers that verifies that transaction A did indeed happen.
Some pretend that only centralised electronic systems are the only ones having costs, while in fact it's far from the truth. Ironically, the credit card game in the US where they jack up the merchant fees way, way up is a counterexample that capitalism is fostering a pro-consumer market (I'm not saying that capitalism per se is broken, it's just the fact that capitalist policies in this area doesn't work out great). In Europe where they implemented caps, "rewards" type credit cards have gone down, but regular credit card and debit card usage have gone up. This is because the "rewards" system isn't pro-consumer, it looks like pro-consumer but instead it actually benefits only those who massively use them to the detriment of others. Unlike "rewards" type credit cards, regular credit cards acts more like a tool that can make or break finances who uses them not correlated to the frequency of use, and debit cards are essentially plastic wallets.
To highlight this, Americans are grappling with Zelle (which is just rolled out) and ACH while their neighbors to the north have Interac running relatively seamlessly and Europeans have SEPA and even some countries have local feeless/reasonably priced quick transfer systems like Swish/iDeal, and discussing how Asians handle their transfer and payments would just shake heads on why those systems aren't available stateside (I'll pick India's UPI and the (mainland) Chinese system as representatives, but that doesn't mean similar systems aren't available elsewhere).