Every business needs bandwidth solutions of some sort. For many businesses that require large amounts of bandwidth finding just the right solution ... from a cost and application standpoint ... can be a confusing process. It doesn't have to be if you understand what to base your decision on.
Like anything in information technology, it really depends on how you will utilize this infrastructure. If you will use them for a small fraction of the day or the traffic doesn't warrant it, it certainly doesn't make sense to provision high capacity transport links.
I think one of the hardest things about this arena is that many times the people requesting the bandwidth are confused about what bandwidth really is. There's a misnomer that bandwidth automatically equals speed. "Well my application is slow, I need more bandwidth". Many times if a study is done on exactly what your needs are, it turns out to be a very different story from the initial conversation.
The best option is the cheapest one that works. Dark Fiber and Metro Ethernet, if an option, should usually be looked at first to establish a price for negotiating. I think you should focus on negotiating techniques that work to bring these bandwidths within affordable reach.
No matter how much bandwidth you are using, you will get a better deal for it at a major Network Access Point (NAP) where you have more bidders for your business, and from which you can easily shift carriers, set up fail-overs and redundancy, etc. Every high end user needs their own boxes to shape traffic at the NAP, and they need them in two different racks connected to two different carriers. Accept the hit of that and you'll quickly see that the ten to thirty thousand dollars a typical urban company requires to get two boxes into a NAP (admittedly on a single dark fiber route) pays for itself in bandwidth charges in pretty much a single year. Even just to PLAN to do it and show your spreadsheet to your carrier, a project that might cost five grand to do right, will result in more than that much per year off your bill.
You demonstrate that you're not a pushover, that you have options, that you understand the options and how to increase the number of options, and you bargain based on the bottom line of the cheapest solution you can find. When they tell you it will "cost too much to have your own boxes and dark fiber to the NAP", you snap back the lowest number you can justify, call it "insurance", and rule it out as a cost factor. When they tell you "our facility is state of the art", GO THERE and count up the number of non-bulletproof windows and visible insecure perches that someone can shoot the servers from, grab the corded phone and walk over to the rack, pulling it right out of the wall and looking astonished: "how am I supposed to give someone instructions over the phone?
Basically, you must point out every deficiency in their facility or service and refuse to acknowledge that your own home-built solution would have any inadequacies, or that the competitors all have the same problems. In a high end negotiation, you must have NO mercy.
By the way, once you've got a contract with your carrier, you must be very nice to them, in total contrast to the way you leveraged like mad in the first negotiation. Don't nickel-and-dime them after you've agreed on terms, don't let your bandwidth payments get late.