Answering your points...
1 Yeah, I really do need all that bandwidth (as you note in your second response, it's for streaming audio). And I probably need more, as should become clear toward the end of this reply.
2 With Shoutcast and associated software, I've been told that a decent-spec machine on a 1 gigabit port can handle the projected load and push the theoretical max throughput of 432gb. (You mentioned 324, so maybe my numbers are out or you typo-ed.
But a one-third difference won't be critical to the viability - but seemingly-common rates of 8-12 cents (or higher), and even your own much lower rate, per gb would.)
3 I'm a marketer and hence don't have the tech knowledge, but would the extra flexibility performance of cloud and CDN services provide an appropriate advantage?
With streaming audio rather than multiple requests for other and smaller files, the server should be able to handle the load (and splitting it between two or even three would likely remove any potential problem). I don't need burstable, and the ability to serve from a few hundred/thousand miles nearer wouldn't greatly improve user experience.
And the pricing would make the project unviable. (Hell, with the required bandwidth it quickly gets that way even on regular dedicated packages.)
4 I mentioned 'probably need more' (bandwidth)... if my numbers are right, that 1 gigabit port can serve 7500 simultaneous users of a 128k stream.
Now whilst that size of audience is uncommon for Internet radio, it's still very small compared to the potential. I can wide-awake-not-dreaming project short-term (maybe an hour a day) peaks of ten-times that... so my requirement is relatively high.
At 100tb-com rates, I can afford ($7k monthly) to have 10 servers sharing the load, and sit there idling much of the time (although there's a not-yet calculated on-demand requirement too for other audio streaming/download).
I don't mind overselling, and accept it where expected - but that won't be with this project.
The promise of 'dedicated, unmetered, unthrottled port' at the stated pricing attracts me - but can it be sustained?