On that topic, could limiting the posting of pictures and asking people to use external picture hosts help with that?
Yes, storage costs matters. I think it’s honestly crazy that Lemmy caches images as much as it does. It would be great to be able to just disable it completely, but alas you can’t do that without disabling uploads for your own users either (at least I don’t know how).
Disabling uploads might be an option. You probably just need to announce it to the people beforehand, but I see most of the people using image links from other sites, so that might not be an issue.
It’s a major downside to my own users though. I wish I could disable uploads for everyone else :P