I'm selling browser extensions on the App Store, but the main money-maker is currently https://soitis.dev/control-panel-for-twitter
When Twitter killed off third-party apps, the browser extension I'd been developing ever since "New Twitter" launched in 2019 suddenly became one of the few ways to make Twitter more tolerable to use, and the number of users of the Chrome version tripled from 30k to 90k in a fortnight (mostly in Japan).
When they confirmed third-party apps had been killed on purpose and jacked up the price of the API to discourage new ones, I started selling it on the App Store the next week and it's made more than $500 per month ever since.
Before the end of the year I'm hoping to roll out a single paid subscription which works across all my extensions when you sign up for it, which enables syncing settings across all your browsers and devices, unlocks additional subscriber-only features, and will enable creation of extension-specific APIs if there are future features which require one. Between Control Panel for Twitter and https://soitis.dev/control-panel-for-youtube I have ~390,000 users, so, y'know, please like and subscribe.
That will _eventually_ include my free Hacker News extension ( https://soitis.dev/comments-owl-for-hacker-news ) so things like new comment counts, user notes and muted users can sync across every browser and device you use Hacker News on.
If that takes off, I hope to make the App Store versions free and figure out how to give anyone who bought it 3 months of the subscription per extension they bought as a thank-you. If anyone's done something like that before, I'd be happy to hear about it via any communication method in my HN profile!