Hi Shay:
BBB itself is open source, so you're free to download it, install it and use it. The costs associated with BBB are: server, bandwidth and storage.
So much of this depends on how you go about implementing it.
I would begin by asking myself:
how many simultaneous users do I expect?
How many rooms will I have running at peak time?
What's my cost, per terabyte, for storage?
Are you building a server on site OR are you using something like Amazon AWS?
If building a server yourself, you need to figure out what kind of a server you need to build to support the number of users, then calculate how much bandwidth you need, plus costs associated with running a web server.
If Amazon, you can price out their various server packages.
To give you a little kind of an idea of what my costs were. It cost me about $200/month just to have the server running and available on AWS. That $200 bought me an IP address with Amazon, a server and storage. Also, that was with very limited bandwidth usage as no one ran any BBB sessions for that month. Your prices will vary.
I also know there are BBB providers out there, but don't know their costs off the top of my head.
There was a document I recall that gave some estimates on per user bandwidth needs, but I can't remember. Was it 1 mb/minute per session?
James