Ordered Crucial 32gb ram at around $158 total.
What RAM did you buy? I contacted Crucial yesterday (21st Oct) because I couldn't find any listed (Apple iMac (Retina 5K, 27-inch, Late 2015)), and they said:
"Thank you for contacting Crucial. Unfortunately, because that system is so new Crucial is still in the process of testing our products with the system. This means we currently are not offering a list of compatible parts. We hope to have this information up soon, I would recommend checking back in every week to see if we have updated the site yet."