There must also be limits to perception or resolution. Are our eyes even able to tell the difference between FHD, 2K and 4K on a 15" screen?
I tested FHD vs 4K on a 31" screen and could not are a difference when watching a 10 minute video (I had 2 screens side by side for reference).
On a semi related note. I also tried watching 60fps videos at 60Hz vs 144Hz (again side by side) to test out my new screen. No difference. Even fast moving things.
I really feel like either I just don't perceive these things and it'll keep more money in my wallet, or that I'm not alone and everybody can save money. A chart of when differences actually become perceptible would be great. It wouldn't surprise me I'd the threshold for 4K were 42", 10bit only in grays and fps at a certain pixel per second movement speed.