The amount of members you have and the type of content you have makes a huge difference in numbers.
I use anywhere from 10mbps to 50mbps depending on the day of the week for each members area. I host the members area with SexTracker.
My front ends use from 10-25 and I host them with National Net.
My program and backend for
Evil Genius Cash is hosted at National Net too.
Most people arn't going to tell you how much bw they use, it's easy to see how big they are that way and most people don't like others to know.