You are failing to price in counter-party risk, exchange rate risk, and myriad other risks. Not to mention the cost of having a whole separate point of sale for a currency nobody has - or the fees for converting it back into a currency you can pay your suppliers and taxes with. Or the cost associated with reporting.

You can pay a very similar flat 1/3 of a cent fee for an instant FedNow payment with none of those risks or costs.

Cash, bank transfers, etc don't price in counter-party risk either. The only thing that does is Visa, and that's a layer on top of your existing statutory rights. Agreed re: fiat onramp/offramp.

0.3c is still far in excess of 0.0025c but maybe that won't matter.

The wild fluctuations in exchange rate and having a terminal for a currency nobody uses are a dramatically bigger risk than 0.3c - and yes, your counter-party risk is a non-issue in legacy finance.