@jume Depends on how expensive the services your admin is using are, but masto.host supports ~2000 users for $90/mo
For someone running a server themselves via Linode or DigitalOcean, it can be wildly variable but there is, to me, no way you'd need to spend more than $200/mo for 1k people. So like... ask your users to give a dollar a month and you should be okay? In my experience, people with more money will give more and offset the people who are unable to contribute
@jume btw costs to run Friend Camp are publicly available though we are only ~60 active users
https://docs.google.com/spreadsheets/d/1mRtQiH1ZeK5HzPnocwfQmUutHVAhpusxcGq44hsKF7E/edit#gid=0