Probably because they love to waste money! Or maybe because it's a status symbol? No way would I spend that much for any jacket!

If it isn't actually raining, you want to wear something a lot more breathable than the so-called "breathable" rain jacket. A few years ago I did a late September hike with temps in the low 40s F (it was low 30s by the time I stopped for the night). It was breezy, and shirt sleeves were just a trifle too cool even though I was climbing, so I wore my 2.5 oz. Montbell wind shirt (breathable but not waterproof) over my hiking shirt. The wind shirt over my shirt lightweight base layer top) was just perfect while I was moving! Of course when I stopped to rest, i immediately put my puffy jacket on top, and took it back off when I started moving again.

You don't want to wear a rain jacket unless it's raining. In fact, if it's warm and raining, I leave off the rain jacket and just get wet, which is still less wet (or at least less slimy) than I'd be from sweating inside the rain jacket!

I pretty much agree with Andrew Skurka in his assessment of so-called waterproof/breathable (WPB) rain gear.