Are my theories behind panel thickness/thinness, quality, date of manufacturing and pricing correct?

When checking out laptop reviews and panels in the HP parts store, I notice that a lot of the 17.3" 4.2mm panels which are in the mid $300s have good reputation for color gamut/reproduction. When I check out 15.6" ultrabook panels, I notice a lot of the 2.6mm panels run between $800 and $1,199, and at least one of these 4K/UHD panels has only a 45% color gamut. Yet the 3.2mm standard HD panels are in the $300-$400 range and have a 72% color gamut. If the world of 2.6mm ultraslim 4K/UHD is so difficult, wouldn't it be easier and better for manufacturers and consumers if HP sticks with 4.2mm panels for their ultrabooks and standard laptops? I'm sure someone will correct me if my theory is wrong. Update: Out of curiosity, I checked the specs on recent 15.6" Omen panels. I was pretty sure they'd be between 4.0-4.2mm, but it turns out they range from 2.6-3.2mm, including a 3.2mm standard HD panel with a 45% color gamut. It's not available to order, so no price was displayed. But I'll bet its price ranges from the upper $200s-lower $300s. Considering its lower color gamut, maybe lower? Considering their 17.3" 4.2MM 4K/UHD panels are better, I wish HP would give us the option to customize a 17.3" Envy without discrete graphics for longer battery life, or else add 17.3" laptops with 4.2mm panels to the Spectre series and include the Ultrabook CPUs, NVIDIA Geforce MX150 graphics, and higher-capacity batteries.