I have MR hocked up to a electricity meter - £300 / year in power to run.
Probably higher now that the prices have gone up.
Running since 2017 - so cost me about £1500 in power alone.
There's no such thing as a cheap server
What is Medieval Realms hosted on?
Yeah, run it on an old cheap computer that you never turn off. It doesn't take much CPU or RAM power for the server to run well and it doesn't need to have a GPU.
I built my own server computer a few years ago for ~$700 and its been a beast for hosting multiple game servers on and much cheaper in the long run than renting a remote server.
Depends. Some older hardware uses a lot more power than newer hardware. What's your server machine's specs?