@woozle @trurl @mekkaokereke @justinmwhitaker @SDFmastodon.host started at around $30 per month on a single VPS, but quickly evolved into 4 then 5 servers, with a monthly cost above $400. I think peak was around the $450-500/month. I got some donations from time to time, max was maybe around $30 iirc, far from getting into sustainable territories, even though super appreciated.
At the time, my servers were receiving more than 70% of the fediverse public posts, I was hosting one of the biggest funkwhale instance, plus a relatively sizeable Peertube one, the Plume flagship ( fediverse.blog, luckily this got separated and given back to Plume community before the break ) and a few other services ( xmpp chat over your mastodon creds, pleroma before it was considered bad, a mastodon public relay, etc.. ).
Most of the cost was the DB server, and then you add the workers, public front, and file server, this adds up fast...
Could I have reduced monthly expenses at the cost of slower service ? Yes for sure... Or I could have shutdown a few services too. Also the time spent maintaining the whole stack of different softs was getting a bit out there too, especially as I was maintaining a soft fork of mastodon to provide search before ES was introduced, and maintained a patch without ES after ES was introduced.
When I decided it was too much to continue sustaining this kind of running expense, I had contact with someone I thought would be continuing for a long time, and would pledge the same I did "If/when I have to stop, I will give the server to another admin the users approve of to continue instead of shutting down". Unfortunately, the service went dark one day and the admin just vanished.
All services/backup/domain etc... were out of reach for me to get control back and save, so it was all lost and users had to move elsewhere with no backups :/
Lesson learned, if I had to setup something again, I would not do it alone but rather with a group of admins, and a clear path to auto-financing the hosting part for long term sustainability.
I was lucky to have a mod team that was doing a great job, having to moderate only as a replacement for them when they needed to take a break or to validate their decision with the admin hat. That taught me also that mod burnout is a real thing, hence the supplementing when the mod team needed help.
Happy to answer any questions you may have :)