The reason to the price difference is because the surface of the LCD screen is larger than on the laptops. Larger screens means larger number of "dots". More dots, means that the % of error is higher. Remember that even if one cell is not working, the whole LCD plate has to be scrapped.
Also, the market target group is not the average home user but to companies or executives. Those tend to have enough money to buy regardless of price.
That is also the reason to why Mercedes are more expensive than a Toyota. =)