I agree with what redpoint posted in post #19. Additionally:
1) You don't always have to be doing high mountaineering, to encounter extreme conditions. I've camped in 80 mile per hour winds in the deserts of Southern California. I've camped when 2 feet of snow dumped on us, overnight, in Yosemite Valley.
2) A $600 tent comes out to be less expensive than a bunch of $70 tents, in the long run. I spent 7 years living outside, traveling. After that, I spent most of the rest of my adult life camping a couple hundred nights per year, or so. I used to wear out and go through 2-3 medium priced tents per year. However, I've had my Bibler I-tent for about 16 or 17 years, I think; it's received far more use than any of the long-gone medium priced tents; and it's still in great condition.
3) A better tent can also come with a better user experience, and that has some value. Less weight and less space in the pack, faster set up and take-down, no flapping at all in the wind, better air flow, less condensation, absolute waterproofness these sorts of qualities can save you time and effort, decrease frustration, increase comfort and rest, etc. How you value them is a personal choice; when I'm going to use a tent for literally hundreds to thousands of times, such things are easily worth the small fraction of a dollar per day, to me.