Here are the big byte users and below is a reponse I recieved from the Joomla forums on joomla.org in case your curious. If thier response seems good to you guys then I guess its good for me too even if it still seems a bit high.
77.30% bytes /joomlatest/administrator/index2.php
These are the top two (for last month) sorted by bytes. Everthing else is less then 5%
2069-reqs 69.04%-bytes .php [PHP]
22615-reqs 13.09%-bytes .png [PNG graphics]
joomla forums response @ joomla.org
Since your normal site visitors will never use the administrator they won't deal with that stuff.
To help with some of the transfer you can go to Modules->Administrator Modules and unpublish items you don't use. I have done this with many things, but only stuff I never use.