I think it's more for existing Notion users that may wish to have a tiny microsite about something. Someone already invested in Notion isn't going to care about self-hosting.
This. $10 a month isn’t unheard of but when commodity VPS hosting is $5 a month (if not less) and stuff like WordPress.com is $8 a month and Netlify and GitHub Pages exist, I don’t know how broad this market is. Especially when you’re talking about the lock-in imposed by using this sort of thing.
You know a site like this can be entirely static and hosted for free with github pages, gitlab pages, netlify, vercel, or any other free static site host.
Notion users will be in for a nasty surprise when they realize that DO is closer to a Raspberry Pi than a OEM PC.
All you get is a barebones OS without a GUI. You have to set up everything yourself: server (e.g. Apache), language (e.g. PHP), database and SSL. This is a non-starter for people that have never seen a command line interface before.