I think in bayarea, the cheapest colo you could find is in Fremont, for $400 per month.
I'd like to use colo, so that I could make a raspberry pi cluster as my server. That will be cool. but $400 is too much for now.
Whereas my current AWS monthly cost is $10.
I try not to use any amazon features to untie from amazon, so I can switch servers later.
This is the cheapest colo I found in Bayarea
http://he.net/Colocation-in-Fremont-CA/?l=Fremont_Colocation...
It seems to be the same vendor for linode
Another benefit for using aws is that you can deploy your server globally, instead of a single location.