A great article from Vijay Gill. Vijay Gill is the Senior Manager of Production Network Engineering and Architecture at Google and we consider him an authority on issues of Data Center Cost Analysis.
Wondering if you should choose a Server Colocation option or a Cloud Computing option for your data needs? While this article focuses on some larger numbers, it could be modified for a smaller situation too.
The author draws an analogy between cloud computing and colocation as Cloud Computing services being the same as utilizing a Taxi Cab service and Colocation being the solution of buying your own car. It really depends on how much you intend to utilize the service.
Vijay ran a comparison using Amazon Web Services pricing as a benchmark.
Additionally, Mr. Gill posted a spreadsheet (on google docs) that details his findings and allows you to plug in your own variables.