>I suspect that most of Apple's "proper computer" sales are laptops where they put a retina display anyway, and if you shell out $2k for a laptop, you can afford to spend $300 for a 4K external display.

My old windows computer is dying and I am thinking about getting a new mac. It seems the choice is a $2200 imac, or a $2700 mbp + a $1000 4k 21.5inch monitor.

LG is one of the very few companies that sells 4k 21.5inch and 5k 27inch monitors. Even 4k 24inch monitors, which I am guessing you are referring to, are quite rare. They are also not really approved by Apple. I mean, 4k 24inch will make everything look too big I assume, and 4k 27inch isn't retina quality.

So what exactly are we supposed to do? There are no external monitors to buy. Apple doesn't sell any, and the 3rd party solutions are few and far between. Maybe they want everyone to buy an imac and a mbp...