“It’s not what you pay a man, but what he costs you that counts.”
Similarly, it’s not what you pay for an OSS but what it costs that counts. Total Cost of Ownership (TCO) is a useful model when evaluating OSS projects because it considers the direct and indirect costs (CAPEX and OPEX) relating to an investment in your OSS.
To some extent, direct CAPEX (hardware, software and commissioning services) and direct OPEX (annual license fees and other recurring vendor support costs) estimates can be made based on the agreed contractual amount. If you have a comprehensive understanding of ancillary tools / services (eg servers, storage, database licenses, etc), then indirect CAPEX can also be estimated. The missing piece of this puzzle is indirect OPEX (CSP staff wages, etc).
Since most vendors claim efficiency improvements from using their product/s as a key selling point, you would imagine that vendors would be able to cite examples. In my years of helping CSPs with their vendor selections, I haven’t seen any benchmark data that provides evidence of efficiency improvements.
And there’s a good reason for this. You need a before and after analysis and it requires transparency from the CSP. It’s not impossible, but certainly a challenge for all involved to audit and prove a track record of efficiency improvements.