There are a fair few who've done it in the Youtube space (the infamous Pewdiepie for example), but no, I don't think I know of any Patreon millionaires yet either.

But how sustainable is it? Patreon is rather simple: Users directly pay the artists, however much they want (and Patreon presumably takes some fee).

Youtube makes artists depend on Youtube's subscription and/or advertisement viability, which are largely outside of the control of both artists and consumers. Consumers cannot control where their money ultimately ends up, artists have little planning security.

> with respect to Patreon

This is important. Typically one would have income from: youtube ads, twitch payout, sponsored content and patreon as a bare minimum. Usually you can add sponsored stuff on instagram/fb/wherever, possibly selling merch. Not to mention the stuff you get without being explicitly asked to endorse it.

Google says there are currently 2.9 billion internet users, if 1% of them pay you 1 dollar you'd gross 29.1 million dollars, 0.1%, moving the decimals even at just 0.001% could gross you a cool 29 grand. That's really not a bad deal.