We don't see BSD deployments thanks MIT licenses, which allow for companies to keep their forks and the old AT&T suit.
The only reason UNIX shops migrated to Linux was to avoid paying for workstations and migrate to Linux.
Companies like SGI dropped their UNIX and are having Linux forks, as a means to outsource development costs.
Likewise with Oracle dumping Solaris and migrating whatever is relevant to Oracle Linux.
In 100% of projects I have been involved, Linux was always chosen as means to reduce license costs, as developers do 100% of their work on Windows workstations.
I have seen the same application with drastically different performance characteristics on different platforms.
Linux is the king on the server because it has been heavily fine tuned for the server over the ages. The cost, while a factor, is not as relevant. Any company deploying large scale applications on Linux has to hire enough engineers to keep it running that the cost of Windows is largely offset. If it were just a matter of cost, we’d see more deployments of FreeBSD and the likes.
It is the same reason people stick to Java despite all its shortcomings.