I do not agree with the litigation increasing the cost of the final product so much, IF we are talking about defending themselves against potential lawsuits. There is deep and very affordable insurance for that, and there are businesses and manufacturers who have a much higher risk in litigation but the end product is nowhere near the cost of a plane. The caveat here is when investors own shares in the insurance company AND the manufacturer who is a customer of the insurance company. Think about how that works for just a moment.
I do agree with low volume being a big component, but the manufacturers themselves have a problem in that they do not invest heavily into more efficient ways to manufacture products. There is no reason that a plane needs to have such a large labor component to be produced. Even if you argue that it does, the closest comparable, the automotive market, has this figured out for models that are very low in volume. There are special models out there that roll off as customs, and have a manual labor component. They are more powerful, much classier, take much more abuse, have (arguably) more complex systems (excluding the panel), also use exotic materials, and do not approach the cost of a brand new 172.
Regulation takes a piece of this. Each and every nut and bolt that is regulated and certified on that aircraft adds to a cost for the manufacturer. You make the yoke? Simple enough piece of equipment. Not necessarily a high cost to produce item, but in the same breath, they are not high volume, either. So a simple item, low volume, but the manufacturer needs to certify that piece separately. There have been comments about the same nuts/bolts at Home Depot, or the same automotive products that you can usually purchase for a few $ at the auto parts store. The same items, but one is regulated/certified, one is not. So you go to the flea market, buy a bolt that looks the same as the one at Home Depot, but truthfully it's a lot weaker because you're not a specialist. Stick the wrong one in, it breaks, and (maybe) goodbye. The burden of regulation for the manufacturing company whether it's for component manufacturers or the actual aircraft manufacturer is a very heavy burden.
Being a publicly traded company is a huge difference. A good private company in manufacturing holds itself accountable to the end user that receives and uses the products produced. When you switch to being public, you are now accountable to the shareholder. Shareholders want returns, and they want them now. "Oh, you found a better way to do things, but it's going to give back less of a margin for a few years until it really starts going? Nope. Keep up the high margins and returns." Every time one of our competitors is purchased by a public entity, we can see it coming for miles away. They get very sloppy, innovation decreases, investment in doing things better decreases, and it's a mess. Sad, really, because we lose a good competitor in the marketplace. Too many of them go away, and we ourselves are in trouble. We need good competition in the marketplace to keep us moving forward and innovating. If we have no (good) competition, we're going to be focused on things that do not matter.
Which brings me to the next point. There is not a lot of competition out there in aviation. Sure there are a lot of airplanes to choose from, but the manufacturer pretty much knows...if you want a high wing, you're going to do X, you would like to have Y, you're a Cessna customer. You want a low wing, you're going to do X, you would like to have Y, you're a "Insert Manufacturer Name Here" customer. Look back through the threads on plane and mission suggestion requests...doesn't vary that much, does it?
I also agree with Sooner and Tampico above.
My .02.