10k, 50k, heck even 100k a year should be nothing to your startup. That's the cost of one good developer. Focus your cost savings in other areas, if 100k is the kind of optimization you need to make (and you're actually spending 100k a year on virtual hardware) then you have other problems.
Its a fair point, but i suspect that moving 100k of infrastructure from AWS to a colo is going to add at least 1 dev-ops / sys-admin (or sucks in 1 developers time). I'm skeptical that the cost benefit comes in until well above 100k / yr.
