If as rumored the first ARM Mac being released this year turns out to be the 24" model (without a larger companion, which would be an interesting change of pace), I imagine it'll be more expensive than the 21.5" 4k iMacs by just enough to cause many to say Apple's being greedy, but not so expensive that someone buying the then-current 27" iMac will feel terrible. "Well I need the larger screen anyway, and this thing will still let me boot to Windows for years to come. I don't want a toyMac".
The rumored 24" will likely include some hardware or physical features that none of the Intel iMacs will have (besides the ability to run qualifying iOS and iPadOS apps), which together with the larger display size will help "explain" why it's more expensive. Nearly edge-to-edge screen and rounded screen corners, of course. Maybe FaceID. Some "first time ever on a Mac" feature other than Apple Silicon, because Apple likely wants their "regular" customers to not really worry about the silicon part. It's kind of like the amount of memory on iPhones and iPads - regular folk don't need that info.
For a while it'll be the only new iMac option, so it'll sell to A) regular people looking for a new iMac, B) enthusiasts wanting a taste of the new ARM Macs and C) people who would
really much rather have a larger iMac, but
really like the new design and "just can't wait, potentially for another year" (and will absolutely post on these forums asking if they should go for it).
After some time has passed (and at least the smaller ARM Macbook Pro has been released) Apple could then release the larger ARM iMac which will be more expensive than the current 27", once again "explaining" the price difference with some physical difference or hardware capability. Same design language as the smaller one, of course. Still not the ARM iMac Pro, though. I imagine Apple will want to prolong the life of the current Mac and iMac Pro as much as they can within the two-year transition period both to build industry confidence in their "more affordable" ARM Macs and to give software developers ample time to port and refine their pro tools. They'll manage that just fine on the smaller iMac and Macbook Pro.
Maybe Apple releases the ARM Mac mini at the same time with the larger iMac, to showcase an ARM Mac at a price point that's considerably lower than all the other ARM Macs they've released by then (quite possibly even in line with the current minis because it'll be lower-powered and headless). It'll look really tempting to a certain segment of potential customers who have up until that point been lamenting how expensive these things are. It'll be a no-brainer for a lot of people.
I imagine the larger ARM Macbook Pro will then follow. It will have been enough time for anyone who would have originally "really wanted the larger Macbook Pro" to have already bought the smaller one because "they couldn't wait", and now they curse and consider switching to the larger one.
Admittedly that's a really wild and odd way to release new Macs, but if the rumors turn out to be true that the smaller iMac will be released without a larger counterpart, it would suggest a staggered transition where Apple seeks to offer only one size of desktop and laptop product at first to cater to both markets. Apple also likes to release products that tempt enthusiasts to buy
now, while the release dates of the products they
really want remain unknown.
This forum is full of threads from those people