The Nordic countries have instant payments. It doesn't actually cost anything extra (just the usual flat fee, maybe $0.20 to $1... although for smaller payments like for a candy bar, you could choose a 0.5% to 1% fee which might be cheaper...), except for companies that gain from rents they charge for wire transfers, etc. Here's an example from the Nordic countries:
https://nordicpayments.eu/p27-the-payment-gamechanger/Actual expert on the topic: "For truly "instant" clearing and settlement the main hope is the RTP network, which already has extensive coverage. (FedNow, its rival, is 3 years away). The Fed can also quicken payments by (1) having Fedwire and NSS operate 24/7 and (2) easing FinTech Master Account access."
https://twitter.com/GeorgeSelgin/status/1356937488871358465?...