I assume you've been looking at offers from hosts like HostGator? These type of hosts are called oversellers. They sell more space than they have, usually limiting your usage by some clause in their TOS. If you realistically need that much space, then you'll need thousands of dollars per month.
What is the real amount of disk space that you currently need?
I am looking for shoutcast hosting 30 @ 56k & 30 @ 128k looking for a good deal