Well one reason is the materials involved and the larger amount of said materials. HyVent is a top material from North Face (breathable and water proof) and goose down always warrants a premium.

Then of course you will pay extra for a proven brand name. On top of that it's season for winter coats, so supply and demand will affect over all pricing as well.

If you want to find a good deal for a winter coat, I would recommend waiting until spring - summer. $300 for a warm sturdy long coat is not that bad, especially if it will last you several years of course. But I can not speak to the specific quality of this coat.