The 27" iMacs aren't using soldered RAM and has 4 slots. So it would probably be cheaper to buy and install RAM separately. 32GB would be about $180 instead of the ridiculous $600 Apple wants.
Can you actually install additional RAM? I didn't know you could take apart an iMac; i thought that changed after their "unibody" one piece aluminum design.
It is by far the easiest! It is a very thoughtful design, nothing like your average PC where upgrading the RAM is the same experience as it was 20 years ago.