Windows 10 is not free. The cost is built-in to the hardware you buy. They threw their users a bone to get some goodwill and hopefully entice some of them off old OSes, but the OS is not free, and this canard needs to stop.
Linux is free. Do you mean to imply that Linux is nothing more than an advertising/tracking platform? I pay for cable TV, so I guess I'm not the product there right? Oh wait, even though I pay the real money comes from being able to direct my eyeballs at ads. The world is not that simple, and I keep seeing people parrot this exact line at everything. It is applicable in some cases and not in others, so don't whip it to death.
Yep, my restore disk set had a bad disk (and I paid for them too which sucks) so since it was the Home version and I thought I might need stuff that Windows 10 Pro has I went for pro, cost me $200 bucks. I got my license on Amazon. I thought about getting an MSDN subscription but not sure how the licensing works these days for the OS's it includes (it used to be fairly complicated years ago).
Edit: I used smile.amazon.com so money is contributed to my charity, the American Heart Association.