> Whoever host the server?

Many are self hosted.

> The difference is instead of only serving 50 people before lowering fps, instead now it can serve much more.

2b2t has 920 players online right now. That's quite a lot for a single instance, IMO.

It is, for Minecraft. But not in the scale of "people who might want to visit Middle Earth Minecraft," or "The Earth in Minecraft", or...

Yeah I mean whoever hosts the server can add some (tiny?) expenses to host a "static" version of their server. Though I'm not sure why spectator mode isn't sufficient.