On the Fireside Fedi interview with Jerry ( the admin of Infosec.Exchange Mastodon instance ) a scary truth was suddenly revealed ( on 34:11 ): Just to keep the instance up and running he needs to spend up to $5000 a month, pretty much out of his pocket. Donations to the instance barely cover any of that. And if he will ask people to pay to use it, they will, rightfully so, switch to a different instance.
The reason is easy: one likes the fediverse, wants to contribute for it and wants to enabled people to use it even if they can’t afford to pay for it.
On a smaller scale, that’s not much of a problem. I’m glad I can host for some people who don’t have money at all. Some of the others donate and some don’t and that’s fine as well.