I asked about this.

Around ~180 euros a month for the server they were renting to run this Lemmy instance. Anybody can host though and any member of a Lemmy can see content and interconnect with other instances.

I was looking into potentially hosting my own Lemmy for my friends and I because the cost would be more manageable.

I'd imagine if people started doing that it would decentralize the costs and the administrative overhead.

similar to old usenet and fidonet, volunteers, there have always been people happy to help run hardware and help make the commons a thing. people were lured away from the gardens and parks by digital theme parks and shopping malls, where the users become customers.

people wonder "how can it possibly work"

email works great! same concept.

Admins are employees. The people running the subs are mods. There aren't even 1% of enough admins to moderate the subreddits, but there are enough to police the moderation stances of the large subs.