There are some 32" 6144x3456 monitors nowadays and they occasionally dip to the $800 range when on sale [1]. But for a more direct comparison, the Kuycon P20 looks very Apple-like, matches the 4.5K resolution of the iMac, and is $799 for its regular price [2].
[1] https://www.reddit.com/r/buildapcsales/comments/1v87f6i/moni...
[2] https://kuycon.us/monitors/P20