If Apple has to spend a bundle on marketing to get the meagre share they have, why has GNU/Linux twice the share? Could it be that its not about marketing only but price also matters?

Parent leans on facts not in evidence. 100 million users of GNU/Linux on the desktop cannot be GNU/Linux freaks/geeks/sociopaths. GNU/Linux works well. If someone with too much cash wants to spend money on CPU power to round the corners on rectangular areas of the screen, so be it. Others want to get on with what they are doing with less regard to M$ and pals bottom lines. I use GNU/Linux because it works and that other OS does not. That other OS phones home, sniffs files for DRM, BSODs, has a very EXCLUSIVE EULA, invites malware in, needs re-re-reboots, and messes up memory, storage and everything else it touches. I do not give a damn about how beautiful the UI is. I use PCs to get things done.

One of the richest companies in the world produces a crappy user interface. So much for the thesis that GNU/Linux must have professional UI designers. Take, for example, GIMP. Many say it has a lousy user-interface. I can give GIMP to folks who have never used PS and they have no trouble at all making the fish larger, eliminating fly-away hair, whitening teeth and eliminating ex-boyfriends. In what way is the UI not good? Only in that GIMP is not identical to PS, apparently. Folks who take the trouble to learn how to use GIMP have no problems with its user-interface.

"Stable" has two meanings: 1)features set 2)failures are rare

Hmmm.

Iraq: suicide bombers, IEDs, AK47s and RPGs

DC: handguns...

That does not look like a fair comparison, especially with bombs that can fly in a window from miles away, killer drones flying day and night and taxpayers tolerating thousands of casualties and billion dollar budgets for occupation.