Putting high-res display and touchscreen does not increase cost on tablets but on laptops it does. WHY??

These days a lot of tablets seem to be getting 1080p or higher displays( android, windows and ios) and still they cost around 300-500$ and notably same as what their previous gen models with low res displays used to cost.

BUT when it comes to laptops, for putting a 1080p or higher display and a touchscreen the OEM's seem to charge 30-40% premium or even more to put a retina display like the Kirabook and Macbook Retina and the Chromebook Pixel.

Don't really seem to understand the logic behind OEM pricing !!