Consumers are determining the direction, not the companies. Most people want thinner and lighter, even at the cost of better picture quality. I went through this as well when looking for a TV and I got a smoking deal on my 34" Sony last year.
Yeild still drives the price of LCD as well. Only a small number of defects are allowed and the larger the screen, the harder that is to do. In order to hit the profit margins, they have to charge more compared to the number produced, so the prices are higher. Over time, production technologies will improve and the cost will go down.