The studio display is basically the same display as in the 27" iMac, with some VERY minor improvements (like 100 more nits and more speakers), but no major improvements (like 120 Hz, or mini-LED).
In the iMac you could get the display plus a whole computer (plus keyboard plus mouse!) for $1800, and often discounted to $1400, whereas now you get only the display for $1600. What a deal.
We can argue and juggle and rationalize the numbers whatever way we like, but the numbers stubbornly remain the numbers.
Amazon currently has Apple's 2020 27-inch iMac (3.1GHz 6-Core, 8GB RAM, 256GB SSD) for $1,399.99, down from $1,799.00. You'll see...
www.macrumors.com