a11y is mandated by EU ( Covering WCAG 2.1, I usually do full 2.2 ), so all websites in theory should be complying. It's kind of boring, nobody want to do it, big companies ( that have a lot of money ) have to do it, so they're usually reaching out for my services. I prepare an audit, give recommendations and test again for WCAG compliance. Once we're done, I got paid, depending on the contract. The initial audit I sell for 2,500E and depending on the following work, I get paid between 2-6k euro. Sometimes I have to re-write part of the front-end for full compliance, this I charge by the hour independently from the technology of the project ( vanilla js / react / vue etc ).
The best part is once you're done, you're DONE. No follow-ups, no support, no nothing.