You're also forgetting re-training thousands of employees on an entirely new operating system. That's far more of an issue than commercial support at this point

You're also forgetting re-training thousands of employees on an entirely new operating system. That's far more of an issue than commercial support at this point (as the argumentors responding to you have pointed out). Even though Unity and other desktop environments are quite intuitive at this point, changing over would cause a massive disruption to laymen who have been using a Start menu, Windows Explorer, and Outlook for years. The benefits of switching (license costs, I suppose) far, far outweigh the benefits.