What exactly are you self-hosting that’s gobbling up that much data? I’ve been self-hosting my website for decades and haven’t used that much over all that time let alone in one month.
Most of my bandwidth consumption is from torrents and downloading Steam games, but even that doesn’t get me to even 1tb/month.
You might be interested in this project where someone has hooked up a low-power system to Mastodon and is tooting through it stories about the experience. The project author may also be worth contacting.