Chances are that your colo datacenter is building out an openstack-based cloud offering.

So you build your colo'd private cloud on openstack, and then use their's to handle surges. As your traffic grows, you add your own gear to handle the base line.

But ~200K per month, you're operating at a very different scale from 2k or even 20k. Having a couple of idle servers 23 hours a day is not wasteful at that scale, unless your CIO is Ebeneezer Scrooge.

Then you rent out excess capacity in some sort of IAAS business model like, oh wait... AWS!

aws is a good fit if you have big spikes and massive lulls.. maybe.