At the time of writing, 30 users on Stack Overflow have more than 500k reputation, and one user is a reputation millionaire.
The millionaire user with more than 34,000 answers has posted only two answers in three months, yet is easily reaching 200 reputation/day on most days. He's essentially able to retire enjoying a generous pension, for he can't much increase his reputation income anymore by posting new answers¹.
The current runner up with currently around 17,000 answers is also earning 200 rep on most days, entirely from votes on old posts.
One 600k user with around 6,300 answers has been not been posting answers for a couple of years, and he seems to earn 200 rep on roughly half of days as well.
I don't think any other site has users who can similarly retire. The [top math user] seems to earn about 30–70 rep/day from old posts, so would probably need about 4× more posts to reach Stack Exchange Nirvana. I did not systematically check other high-activity non-SO sites.
Based on voting patterns for old posts, how much reputation and how many posts would a user typically need, such that their expectation value of daily reputation earned from votes on old posts is approximately 200 rep? The answer would likely depend on the site, and probably hasn't been reached by anybody on any other site than Stack Overflow, but estimates could still be extrapolated. Of course, it depends on the quality of the answers as well, but those stellar users surely all provide very high quality answers.
¹But of course we all hope that he will not retire and that he will rather sustain his brilliant contributions to the site!