Cloud calculator

Google cloud, AWS and Azure move aggressively and show customers the benefit of moving all services to their cloud. Loads of tools are included in the offering and the customers can do more or less the same thing as they do with Red Hat products. We all know it is not "the same" but there is a discussion we need to have when it comes to cost. Does someone have a calculator where it is possible to bring out ROI numbers, compare cloud this with that versus data center etc. Why install OpenShift on for example AWS when all the tools are already included in the AWS offering and what are the real cost?

I have seen the Red Hat slides with fancy numbers and 523% ROI and bla. bla. but I would like to see the actual calculations that led up to these numbers or the customers will suspect Harry Potter has been involved.

Does anyone have any form of calculator we can use ?
Grateful for any feedback.
//Joachim