You're completely wrong here.
If you were talking about a normal, competitive industry like cars, you'd be correct: reliability costs money, and unreliability costs customers. Detroit knows that lesson all too well. Sell someone an unreliable car, and they'll badmouth it and start looking for another car in the same price range with a better reliability reputation. This is why Japanese brands have commanded higher prices than similar American cars for a long time; it takes a lot of time (esp. in the car industry since people keep their cars for years) to fix your reputation. It's even more pronounced in other markets where the products cost less and people don't keep them as long (cars are the second-most expensive items consumers typically purchase, behind houses).
Microsoft does not operate in a competitive industry. If someone thinks Windows 10 is unreliable, what are they going to do? They could buy a Mac, but those are much more expensive than Windows machines; you're not going to get a Mac for $300 or $400. And the Mac won't so easily run their Windows software, unless they run it in a VM (like with Parallels) but then they're still going to have the same unreliability problems since that's really Windows. They could run Linux, but there again you have the software compatibility problem, and on top of that most people don't even know what Linux is. In the enterprise space, it's really worse because even though they have professional IT, those IT pros only know Windows (you'll have to lay off your whole IT department and start from scratch to switch OSes), and they run all kinds of crappy "enterprise" software that only runs on Windows.
So, since the customers aren't going anywhere (except holding out with their older Windows versions as long as possible), what incentive exactly does MS have to invest in reliability? None. It's really a waste of money for them, and hurts their profits. It's better for them to make Windows as shoddy as possible to save money (while not making it completely non-functional because then they can suffer class-action lawsuits, returns, etc.), and keep profitability high while letting the customers suffer with unreliability.
So, since the