The economics of scale mean it is usually cheaper to get Windows "pre-installed" than no operating system, unless the computer model happens to be very popular for Linux (such as server systems or tiny PC's).
And it is also cheaper to buy machines with "trial mode" apps - because the vendors actively pay manufacturers to include limited versions of their software as advertising. So when you buy a machine that comes with a "free 3 month version of XXX anti-virus", the XXX vendor has actually /paid/ the manufacturer to include the software that will pester you with demands for money after 3 months unless you know how to uninstall it.
My point was that you don't get /MS Office/ for free - you always pay for that in one way or another, even if you get Windows "for free".
Yes.
Yes.