I'd suggest that a big reason for the success of AWS is not the efficiency of their data center operations, but the quality of their software. AWS is a software company that happens to sell cloud software. The pricing of their core services is not necessarily lower than the IBM/Google/Microsoft equivalents. People choose AWS because of the breadth and depth of the ecosystem compared to Google/IBM/Microsoft.

The old quote "Nobody ever got fired for choosing IBM" had some truth to it, as IBM was the safe default choice. In the cloud, the truth seems to be "Nobody ever got fired for choosing AWS". AWS is the safe default choice... you'd really need a good reason to go with IBM in the cloud.