I ordered "only" 64 GB
To answer the question from the thread title:
My 2014 iMac Retina starts to show its age, so I do not want to wait another 1-2 years before a Apple Silicone iMac is available. Beside that I occasionally need X86 virtual machines (Linux & Windows), I hope there will be some kind of emulation technology for Apple Silicone, but I do not want to bet on this.
I ordered the i9 (because I can use the extra cores when running multiple VMs at the same time) with 64GB RAM, 4TB SSD and the 5700 XT (to be future proof and just to be sure, because I do a lot of RAW development). I am planing to use this machine at least as long as my 2014 iMac, after that it will be my secondary desktop computer (currently an 2010 iMac). When I get 10+ years out of it the price is still high but justified.