@everyone complaining about RAM: you can configure that machine with 128GB ECC RAM. You are never going to fit more then that with 4 slots anyway. So all this talk about future proofing or upgrade ability is total noncense. It made sende a decade ago when RAM capacities have doubled every few years or so and prices were going down. These days, you can get the maxed out config from the start. There is nothing to upgrade to. Or are you seriously going to tell me that you are going to get 32GB config now just to spend around $1600-$2000 on a ram upgrade two or three years down the line? Yes, that’s how much this ram costs on the market. And don’t kid yourself expecting it to get cheaper, the market is way too niche.
I think the point being made is that where you can buy a regular iMac with 16GB RAM off the shelf and then later on down the line chuck some Crucial sticks in and bump it up to 64GB for a fair price, if you want to get a 128GB iMac Pro, you are going to have to spec it at the point of purchase and then pay Apple's enormous RAM tax! You can't upgrade the memory once you have the machine on your desk.