Third party monitors which have 1K less pixels is hardly cutting corners. Like I said majority of people won't even notice the difference. Compared side by side the iMac 27 display looks identical to the XDR display in performance.Choosing a monitor with 1/3 less pixels and half as bright, doesn't make it any more reasonable, you are just willing to sacrifice features you don't feel you need in order to cut corners.
I'd bet the profit margins on a $799 4k/144hz Dell are probably far higher than the ASD, because it doesn't have a processor, doesn't have a CNC'd chassis, doesn't have a fancy speaker array, doesn't have a decent webcam and uses the same bulk display that hundreds of other computer makers use.
That doesn't mean they aren't decent displays but if you want better than "decent", you pay a premium.
Apple products are rarely cheaper than their nearest competitor, never have been, never will, but they'll look nicer, have far better build quality and most of the time perform better.
If you take your example it is Apple who are cutting corners by not including Pro Motion and HDR. Two features which should be first on a spec sheet in 2022. Difference is other manufacturers without these technologies will price them lower accordingly. Apple goes the other way and sends out a monitor at £1499 missing basic features which should be present in today's monitors.
The processor inside is just a gimmick judging from reviews it doesn't even perform as it should do because the webcam has been reported to be poor. A £600 LG monitor will have 4K HDR and 144Hz take in to account the aluminium chassis and the speakers etc the Studio Display is a £999 monitor including the obligatory Apple tax not £1499. The Studio Display doesn't have a fancy proprietary panel from what I have read, its likely the same LG panel they have been using in the iMac for the last 6-7 years.
Apple build quality has seen a downward trend over the past 10 years. Need I remind you of the butterfly keyboard, peeling MacBooks screens, bending phones and iPads etc. In terms of their displays, the iMacs that I have purchased since 2013 have all had to have their screens replaced after the corners started to exhibit screen burn.