Managing Bandwidth and Bandwidth Costs?

azav asks: "The company I work for has bandwidth requirements that occasionally spike to satisfy the immediate requirements of a several meg download to say 30,000 users. We hope to make this several million in the future. With that in mind, this request is directed to any person who manages a site that must deliver content on an irregular schedule. How do you manage your bandwidth costs? How do you manage the availability of bandwidth?"

"I'd like to illustrate the second concept. When you have your (for example) T1 and you're not really using it, you are still paying for all that bandwidth. It's like the car that sits in your garage, you're still paying insurance and car payments on it even though you're not using it. But then you put up a new game, serve new media or suddenly become the 'Site of the Day' and your bandwidth is flooded and maxed out. For that case, it's like you've bought a car that only goes 40 miles an hour but while the demand exists and only while that demand exists, you need a car that goes 150 miles an hour. You don't want to pay the money for a car that goes 150 because you only need it occasionally. Later, you know you'll need that car to go 220 but you're not there yet.

So if this makes sense with regards to bandwidth, it is like you'd want burst-bandwidth depending on need. Do any of you face this problem? If you do and have solved it, I'd love to hear about your strategy. Once this is solved, we get back to the first question, how do you manage that cost, put a number on it and either fit it in to your business model or pass it on to your customers?"