For savvy Linux system administrators, 700GB of traffic may be purchased for as little as $100. See http://www.rackshack.net/ . Companies offering staff-access-only, "in-house" dedicated servers enjoy several cost advantages over the old business "Exodus" model of expensive, high security buildings with leased cages.
For those who are not able to put in a few hours a month in maintaining and administrating a Red Hat Linux server, other options exist, including arranging for a system administrator to maintain a server on your behalf. I typically perform these services for $200 to $300 per month, depending on the specifics.
I think you might also find that Sprint's business DSL service offers lower bandwidth costs that Speakeasy. Last time I checked, they offered 6 Mbit (5 Mbit down, 1 Mbit up) for $160 per month, with no bandwidth restrictions.