Well, I'd quite disagree with the server being "about the same" as the client in CPU demand. I don't know how the server works "under the hood", but I assume that it doesn't do client-side stuff like physics processing and 3D calculating etc. I think it just takes data from people and delivers it to others, with some server-side variables which it calculates. But as I said, I don't know.
Someone please enlighten me!