These are just calculated with BOM cost and Apple's margin. Ignoring yield issues at 30" which would likely bump it to $1299 if not a lot higher.
Unfortunately high PPI LCD screen are not getting investment anymore. All of them are going to OLED. You will need 8K TV at 40" to get 218PPI. I seriously doubt that will come anytime soon. Which means there isn't any projection of these Display getting cheaper.
That said, at ~24 inches there's no way I'd buy it at any price, unless I was in a pinch somehow.
So yes, very unfortunate economics. Although one could argue Apple lower than margin, but generally speaking that I not how business works.