Most organizations that decide to move workloads to the cloud are missing a crucial piece of information: What it costs to run the system on-premise. In a viral blog post, David Heinemeier Hansson shared his specific calculations for Basecamp and HEY. Moving back from the cloud makes perfect business sense for him. Of course, your calculation will be different, but unless you know what it costs to run on-premise, you are comparing an uncertain cloud cost with a completely unknown on-premise cost.
As a CIO, you are expected to make sound business decisions. You can only do that if you have both numbers.