So basically what you're complaining about is that high-end products are expensive? How many 4k IPS displays would you have found at the $500 price point even a few years ago?

Irrelevant, the point was that they are hardly “affordable”; if you’re going to get more than 1 external monitor, viewing angles are going to be a concern, and that leaves IPS as the only viable option.

I’m personally running 3 24” external monitors, and I’m fairly sure that I’d have a viewing angle issue had my panels been TN.

Why are viewing angles concern with a multimonitor setup? Don't you turn every monitor to face you directly, so that the viewing angle is 0?

This is what I do with two 1080p monitors; I don't need IPS at all, since I'm always viewing them close to perpendicular to the screen. Has worked just fine for me the past couple of years.

How is IPS high-end, exactly? It's table stakes for the modern-day. The technology is over a decade old, and TN is a strictly worse tech. If it isn't cheap, it should be cheap.

And ultimately this, there’s no way 4K 60Hz IPS panel could be described as “high end”.

High end for 60Hz these days is OLED, IPS is the de-facto standard, and TN or VA aren’t worth buying.