I never intended it to be a side project, I just liked the extension and started contributing heavily to it, to the point where I became the maintainer for the next several years.
I get about that amount per month in GitHub Sponsorships. Not nearly worth the amount of time I put into it, but it’s relatively effortless work. It makes my regular work on other GitHub projects more enjoyable (due to the features that Refined GitHub adds)
The fun part is that they completely botched an experience that iOS can delivery natively. I built a mini app to extract the HSL stream from a URL and have iOS play it. It usually solves my problems with it: https://arte.vercel.app/
Look into chrome.storage.session, they created it explicitly to allow in-memory storage for those scenarios. Not as easy as just setting a property, but good enough.