It would be great if Apple offered more than two monitor options, including one that matches the Mac mini in terms of budget.
I can't see Apple offering an alternative, lower-end display that isn't either an expensive 220ppi panel
or an overpriced 4K UHD screen.
There are plenty of affordable, third-party 4k UHD displays that are perfectly suitable for an "economy" Mac Mini setup - not to mention virtually any 4K TV with HDMI. Unfortunately - thanks to a couple of widely shared online articles with big scary enlargements of "artefacts" & Apple's confusing way of describing screen modes - there's a lot of exaggerated FUD about 4k "not being suitable" for MacOS.
Bottom line: The "looks like 2560x1440" that gives the "correct" UI size at 4k@27" is actually 5120x2880 downscaled to 3840x2160, and shows far more detail & less pixelation than an actual 1440p display, and Apple themselves have been using similar fractional scaling as default on some MacBooks for years. It takes seconds to switch to "looks like 1920x1080" mode which is actually pixel-perfect 4k with a somewhat large - but perfectly usable - UI if you need pixel-accurate.
Yes, a ~220ppi screen (5k@27", 6k@32" or 4.5k@24") is optimum for MacOS
if having exactly the same UI size as the former 27" iMac is vital to you - but there's clearly no demand for 220ppi in the wider PC world*, so that's always going to come at a hefty premium. 4K is a sensible compromise - esp. if you want a multi-screen setup, considering you can get 2-3 4k displays for the price of a 5k.
I suspect that the only reason that there is a Studio Display is that it doubles as the ultimate Thunderbolt charge/docking station for a MacBook Pro, which is a far larger potential market than just Mini/Studio users.
Then, of course, there's the M4 iMac - personally I don't want an all-in-one, but its an option if you really want a smaller/cheaper 220ppi display. If Apple
did release a screen-only version it would probably look like poor value c.f. an iMac - but at least it would be something unique to Apple.
(* various alternative 5k3k displays have come and gone over the years - none have hung around - and even ~24" screens at 4k seem to be getting rare. 220ppi being a "sweet spot" for the UI is entirely a MacOS quirk, and 4k on a desktop display is close-enough to "retina" at typical viewing distances that going higher offers rapidly diminishing returns)