Sure. But that doesn't get over the law of diminishing returns. It might not be 4K that, but would you buy 8K or 16K because "it's the monitor I'm looking at", when the only thing it does is waste CPU/GPU, resources, and battery -- for angular resolution lost to the human eye anyway?
Personal experience tells me that the resolution difference between 4k and lower resolutions (for the same size screens) are Very Noticeable on my 27 monitors. (I have one 4k and one 1440p.) Text is noticeably easier to read on the higher resolution monitor. I think this is primarily because we sit much closer to monitors than to TVs. (I don't think I can tell when my TV plays 4k vs 1080p, as I sit about eight feet away.)
If I had a 30" monitor with 8k resolution, I would probably not be able to tell a difference, unless I went looking very closely to it, so I don't think I'd spend the money on that. However, at 40" or 42", I suspect one would notice it at the distances one normally sits from a computer monitor. At that point, my reason for not buying it would be that I can't afford it. ;)