There's no advertisement (neither does he advertise nor does he accept advertisers), no merch, he doesn't commercialize his streams, he doesn't release updates as much as he should to gain attention (sadly), he doesn't sell the game on steam, he doesn't really charge people for early access - he indeed doesn't make people pay for the game at all.
Microtransaction would surely be predatory, but as said, I'm sure many actual companies/devs would try to add premium content into the game, if they had such a huge audience, that's obviously willing to pay.