Earlier quoted context omitted.
It's not that resource hungry anymore. Hovering stably around 500M RSS and 8% CPU for me right now. That's with ~25 users and a lot of federated, public rooms, some of them quite large.
What CPU are you running it on and how many cores are being used? Are you also in really large rooms like Techlore and Matrix HQ? Because I think I'm in all of the largest rooms (and a lot of the smaller ones)
If you want to go cheaper and have only 300-400 Mbps of bandwidth, I've heard lots of good things about this provider: