Disclaimer: I wrote this article and made this website.
There was some talk of this issue in the recent fediverse inefficiencies thread. I’m hopeful that in the future we’ll have a decentralized solution for file hosting but for now I deeply believe that users should pay for their own file hosting.
Because that’s where all the users are. The “social” aspect of a “social” network. Anyone can host a forum but it’s useless without users.