Earlier quoted context omitted.
Kubernetes is only the software layer, a lot of the cost is in the hardware/infrastructure, and in the salary for those experts.
Agreed 100 percent. Software is the easy part. Getting HVAC, power and network up to the levels of cloud providers is difficult to get right and prohibitively expensive. For instance, the cost for a pair of redundant symmetric gigabit fiber is in the thousands a month and may require tens of thousands of construction costs. These quickly add up, and the upfront costs can quickly reach six figures.
You can always save by going on-prem, assuming you have no uptime requirements. But the moment you sign an SLA, those savings go out the window.