Where are you finding these inexpensive 5K displays?
True, but turns out that a 27" 4k UHD display viewed at 21" meets
Apple's definition of "retina" in that the angular size of individual pixels is at the limits of human vision. So going above 4k in a 27" desktop display rapidly takes you into diminishing returns. Sure, Apple's laptops have higher pixel densities, but they're designed to be used at about half the viewing distance.
...and there are
plenty of 4k displays at a fraction of the price of Apple's offerings. Plus lots of flexibility in terms of size.
5k @ 27"
is the "Goldilocks Zone" for MacOS displays, and to get the system font/icon size "just right" on 4k@27" needs non-integer scaling which results in a slightly 'soft' display c.f. 5k and puts a bit of extra load on the GPU - which might have been a problem for Intel integrated graphics but isn't going to bother a M1 Pro/Max.
I've currently got a 5k iMac and a cheap'n'cheerful Dell 28" 4k side-by-side and the only
obvious difference, unless you deliberately go looking, is that the cheap'n'cheerful TN panel on the Dell can't pretend to match the colour gamut of the Mac - but it's perfectly sharp enough, and affordable 4k displays with better colour are available. Plus, even at 28", unscaled 4k UHD is usable by anybody with good enough eyesight to worry about the difference between 4k scaled and true 5k.
Then there's all the other third party possibilities: ultra-wide displays, multiple, smaller 4k displays, 32"+ 4k displays that you could move further back to keep in the "retina" zone and/or comfortably run in 1:1 mode to avoid scaling.
Apple are charging an arm and a leg for the very narrow advantage that 5k has over 4k. Also, their "studio" display has an awful lot of "consumer" features - particularly speakers & mics which will be inadequate & redundant in any "studio" where audio matters. It's more of a MacBook docking station for the office.