Comment by PhilippGille

Currently this is for payments with stablecoins.

For Bitcoin / Lightning these kind of pay-per-request API paywalls have existed for many years already (e.g. my own from 8 years ago [1], but others as well).

Flattr [2] existed for non-crypto micropayments.

None became mainstream. I think the friction is always the extra setup on the client side. In all 3 cases the user (API consumer) has to set up a special wallet (browser extension or something for the agent) and deposit some money/crypto on the client side first. This part needs to become simpler.

[1] https://github.com/philippgille/ln-paywall

[2] https://en.wikipedia.org/wiki/Flattr