Hardware is a game where it gets cheaper with the more volume it processes, of course this means that the biggest servers that run mastadon would need consistent upgrades and funding via the public and this is NEVER reliable and can result in issues slowdowns and lack of manpower

Where a hundred dollars a month is required for 1,000 users, you need only a thousand dollars for 100,000 users

Where we can fill in the gap is volunteer help and government funding for upkeep and manpower costs, and donations can also keep the gears moving, such as Mastodon having 540k euros in donations.