Amazon did a great job by providing an online calculator for AWS; resides here: http://calculator.s3.amazonaws.com/calc5.html
Which really helps to find your way among a swarm of cloud options.
Is there similar a tool for GAE (Google App Engine) or Microsoft Azure?
Microsoft will have a calculator and other tools around PDC. newdesic has a tool that you can use - http://azureroi.cloudapp.net/
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