mack - 5:15 pm on Dec 10, 2011 (gmt 0)
One option open to you is to try and minimize the total bandwidth. This depends on the specific site, but by simply cleaning up code you can reduce the page sizes quite considerably.
Ages ago I used a CMS that created static files. It was template driven and bandwidth was indeed getting to be an issue. By simply removing whitespace from the template files I was able to see a bandwidth drop of 20% with traffic levels remaining constant.
The same applies to dynamic sites. If you can reduce the overall file size of a page load you will be able to serve more pages without the huge leap in bandwidth.
Its something well worth taking into consideration.