Hard to Calculate Total Cost of Ownership, Return on Agility

"In the many meetings with customers in which I have done a deep dive on their architecture and applications to help them create an accurate cost picture, I have observed two common patterns: 1) It is hard for customers to come to an accurate Total Cost of Ownership (TCO)  calculation of an on-premise installation and 2) they struggle with how to account for the “Return on Agility”; the fact that they are now able to pursue business opportunities much faster at much lower costs points than before," says Werner Vogels, Amazon CTO.

Amazon's TCO white paper attempts to quantify the return.

Capacity vs. Usage Comparison