Ok, it's still early days but yesterday I did just over 1Gb that's with maxplayers set to 16 and elim 60 but the server was by no means full. Comparing my server stats with others on Gametracker I reckon that it could go up to about 3 times that if it got really popular, so very roughly I'd say 90GB a month should be enough for even a popular public server. It's looking like I could downgrade to the entry level server with a 150 GB limit.
Incidentally, I haven't seen CPU or memory usage go over 3% that's with 512Mb available (swap space has never been touched) so again, my cheapvps 384Mb Linux server with free memory upgrade seems to be well over spec. NB I suspect that rescource requirements for a windows server will be a lot higher.
I'll wait until I have a full months data before making any changes.
