LCDs fail like that. While you can check on the price of the panel, here it's more than a new set.
I'm sure you remember the cost of the CRT (tube) replacement. It was so high, no one did it.
I have a 7 year old flat screen with two small green spots at the bottom of the screen. It started with one, then went to two. It goes and comes. The spots are irregular and about 1 inch. Other then that, it's still a great TV. It is a model no. 650 series 6