Personally, I view this issue through what I think are slightly less complex optics; I focus less on the resolution or the price, and more on the practicality of the physical device sitting on a desk. (Not that those former factors are entirely without value... but rather, that I value the latter more.) Based upon that metric, I feel that the 27" iMac is and always has been the absolute perfect size for a computer display... and I say this while sitting at work in front of a set of (older) 30" displays. (No, I didn't get to pick them out; inherited from the previous occupant of this desk.) I don't honestly think that most people have had the opportunity to sit in front of displays of this size for long periods at a time, so I would offer this anecdotal take: understanding that they're not Retina (obviously) and they're 16:10 rather than the usual 16:9... but they are nonetheless
freaking massive space hogs. I mean, they're also not necessarily
bad displays
, per se... but they simply take up an unreasonable amount of space on my desk, for what they offer.
My 5K iMac at home, however, takes up just the right amount of space for a computing device, in my opinion. And the fairly inexpensive
27" 4K display sitting next to it is a pretty decent compromise for the price, between the cheap junk that most PC users buy and the unobtainium that are embodied by most 5K and 6K displays.
So really, I think that Apple did a fair amount of research when they developed that 27" form factor, years ago, and I think they also know full well that a 30" or larger iMac just wouldn't make fiscal sense to most customers... but then they kind'a developed themselves into a corner with that 24" Silicon Mac, because how do you work a 27" Silicon Mac back into the product matrix alongside that?
It's a bit of a sticky situation.