Re: "not because of any technical reason"
"Assuming you mean licensing and not TCO"
I mean both - Linux is still cheaper, especially at scale.
"it's only free if your time has no value "
Our time has value, but Linux is still cheaper. Remember that software licensing itself requires time to manage and audit, and lots of valuable company lawyer time to negotiate contracts. Linux doesn't need any of that.
The majority of our workload runs on Linux boxes, so we have around twice as many Linux boxes as Windows. The Linux team is smaller than the Windows team. Less people managing more kit. How is that higher TCO?
"and you don't need long supported OS version lifetime / enterprise grade vendor support..."
We don't. 1000s of nodes and we manage to keep everything running smoothly and securely. If we really needed vendor hand-holding we'd only buy it for the small dev network anyway so that would keep the cost down substantially over doing it for the entire infrastructure. That's an option you simply can't do with an old-fashioned rigid and restrictive licensing regime like Microsoft's.
Where Linux is more time expensive is that a big deployment tends to be a bit more front-loaded. In terms of central auth, config management, monitoring, patching, etc. it doesn't take as long to set up a Windows network compared to a Linux one. Even taking that into account though, the benefits above still far outweigh this drawback.