What do you consider significant? If you are doing over 10TB then you'll be paying lower and even lower the higher you go. This doesn't help the smaller players doing under 10TB. Do you know of people under 10TB that have negotiated better rates?
I don't consider $900/month in bandwidth significant. And I'm sure Amazon account managers don't either -- but it can't hurt to ask, especially if you've got a growth plan that makes sense.
At that point you're rapidly approaching the scale where cloud-style on-demand provisioning isn't really helping you (unless you prefer AWS's tooling to any "private cloud", which is legit), and you might as well put a bunch of dedicated servers in colo, right?
That is to say, the reason you can negotiate a discount once you get well past that point (or if you intend to grow well past that point) is because staying on AWS makes increasingly less sense for you.
Depends on the situation - a bunch of dedicated servers means a sizable shift from "operating expenses" like AWS fees to "capital expenses" for hardware. It also means shifting expenses from monthly as-you-go to mostly upfront.
Right now I use 3 Softlayer virtual servers to serve up 15TB of static files a month. It costs me a whopping $168 a month. The same 15TB on AWS would cost $1325 a month. I consider saving $1157 'significant'.
Softlayer no longer includes 5TB on every virtual server and their bandwidth is equally outrageous so I'm still evaluating a plan for new servers.
