The problem is: most of it you can do in Linux without any problem. But the issue is that there is no single point of configuration, and it takes alot of manually setting up.
Linux is free as in beer, but when it comes to setting up an equivalent of a forest and domain, and attaching desktops to it with the features you mention, I cannot see how you would be able to do that in less than a day without preparation. Setting up an AD environment including desktops and laptops with suitable policies would take half a day, with half of that spent on looking at the installation progress bar.
Windows isn't cheap in licensing, but I don't think that Linux is currently cheaper if you need three expensive Linux consultants to do the same one MCSE can do in one day, and continue needing them to do simple tasks as adding a new machine to the domain.