I know for a fact that I can run an instance with 15k users and if each one paid $10/year I could make enough to make a living, hire someone to help with moderation and would let me have time to contribute back to the codebase and work on more fediverse projects.
The beauty of this is that I don’t need to have a “huge” site or a monopoly in the market. Other developers could do something similar, due to federation there could be space even for collaboration and/or expansion into other segments.
All we need is to get more people to understand that paying $10/year for something they used to have “for free” is a lot better than having your data exploited.