The goals of a hardshell are to be waterproof, breatheable and tough. Some compromise toughness to get more breathability, some go the other way.
The main reason the hard shells are so expensive is the cost of the waterproof, breatheable liners--Goretex or E-vent. I don't think Gore lets anyone other than Gore itself attach the Goretex liner to the outer facing fabric of the jacket.
On Arcteryx shells you also pay extra for craftsmanship/quality control/warranty. I don't percieve the other high-quality brands (Mountain Hardwear, Outdoor Research, Maramot, TNF (some garments) as charging quite as much of a premium, at least not when you are looking at the post-season sale prices.
Patagonia does not use goretex or e-vent (their product is called H2no, or something like that). TNF uses its own "hyvent" on its low-to-middle price gear, but goretex on the high priced stuff.
I usually ski in a Burton goretex pro shell jacket that I picked up on sale a couple of seasons ago for around $200 US. It does fine by me. I also own a Montaine e-vent jacket that I use occasionally when I think I will need more breatheability, but conditions are not right for a soft-shell. I agree with Alexzn and Matthias that soft shells can be more breathable than a Goretex or E-vent hard shell (and cheaper), but they are not as water proof.
I prefer to wear fleece as a mid-layer under my hard shell (not a soft shell). Why? Because fleece breathes very well, better than any soft shell that provides comparable insulation. When I come in to the lodge after skiing bumps on a cold day, the inner face of my hard shell may be wet/clammy (which shows the hard shell isn't quite breatheable enough, despite the fancy fabrics), but my skin will be dry, which is the key to staying warm. Some folks seem to prefer down sweaters as their mid-layer, but the shell that the down is encased in isn't particularly breatheable (compared to fleece), and down may hold some water, so I stick to varying fleece layers. Cheap and effective.
If you have any interest in learning about the theory behind layering under a shell, check out this blog: http://www.verber.com/mark/outdoors/gear/clothing.html
Good luck making your decision.