My understanding is that as the rules are currently written, GA aircraft of the C-172 weight class have to meet certification standards that apply to bigger/heavier airplanes. There is no differentiation. This is where a vast majority of the development cost is tagged on. Plus there has been no real revisit to the rules in decades to take into account new manufacturing techniques, technology, etc.

Look at a new C-182, there's probably no more than a few thousand bucks worth of aluminum, and it's using a 1940's era engine with mechanical magnetos. Yet a new one is almost a half million bucks. I'm not saying gov't regulation and certification standards haven't helped improve safety, but the free market has a way of taking care of that too.