To be honest, I couldn't tell you-- for the amount of usage that I have on it, it's a flat $20/mo, and I believe I have something like 20G of HD space and 200G of bandwidth, which I've never come close to using up (it's amazing how small your OS is when you're not running a gui).

The really nice thing, imo, is the fact that you can pay a couple bucks per month piecemeal to increase any one stat of the machine as you need it.