The Flash Communication Server comes in three flavors: Developer, Personal, and Professional. Choosing the right license depends on your application and content. If you want to stream pre-recorded video to hundreds of users or carry on a simple two-way chat, this article is for you.
Download this PDF, written by our own Chris Hock, for all the details.

And i thought you had some formula for actually calculating bandwidth!
Silly me!
The PDF contains the formulae!