You could always pair a Mac mini with a third party display even when the 27" iMac was available. It's nothing new, so your assertion that "You actually have a choice now" doesn't make any sense.
The Studio display is practically identical to the panel that was on the 27" iMac. It's simply a money grab from Apple, you have to be delusional not to see this.
Long term, apple loses money on this, because they don’t get every monitor sale, and not every box will be purchased with a new apple monitor. People will keep existing monitors and buy new boxes.