Hosting, marketing, other promotional stuff (conferences, maybe other?), there are still three people on the payroll and otherwise I don't know (which was part of my point) as I've never run a business like this before myself. Oh, subscriptions to AI services... that's pricey I hear ;)

Hosting for their documentation would only be a noteworthy amount if they chose to host on Vercel. Other than that it's a Hetzner box at $100 per month tops.

20% of payroll would cover all that, disregarding marketing which a project like tailwind doesn’t need IMO.

What marketing? Their only marketing is a link in their documentation.