During the launch, Apple generously rewarded it with the title "best Pro display on the market" and directly compared it to a 35k Sony reference monitor.
The problem is, Apple's screen is unusable as a reference monitor. The screen is not uniform, has a strong "vignette". The backlight zones create blooming artifacts. Color accuracy is fairly good, but not better than something found in a low-end BenQ.
Not only is it not the best pro monitor, it's not a pro monitor at all. It literally cannot be used as a reference monitor. It's basically a 6K LCD screen with all the problems that come with LCD.
You can't; that's the point. There are no 6K monitors besides the ridiculous Apple one and the Dell 8K probably needs to be run at 2.5x which I don't know if macOS even supports.
If it's actually the best in enough areas to make it worthwhile, then that's great, and maybe it is worth the cost to some people. Maybe something like the Dell 8k monitor is a better fit for more people in the market for one of these, at a cheaper cost ($4k with a stand), more pixels, and similar feature set (if lacking some named features). Maybe not. I probably don't know enough to accurately judge, but it sure looks like Apple's trying to fleece some people that want the brand name to me.