> There are huge savings in only buying enough bandwidth to handle, say, your 95% load and not enough to satisfy all of your customers at once.

It's bad engineering to run your links hot at 95%. (Here's looking at you, Comcast)

You want to keep link usage at under 50% in order to have adequate margin for growth, be able to fall over to your secondary links without saturating them for maintenance/repairs/emergencies and handle microbursts which don't show up on the 5 minute average timescales monitoring is done at.