This list is a joke, that's not even close to a 1:1 comparison. It looks like they intentionally picked the most expensive options for everything. You don't need a $160 AIO water cooler, a $250 1000W power supply, or a $650(!?!?!) motherboard. The Vega in the iMac doesn't compare to a 1080 at all.

To anyone with an understanding of PC hardware it's clear this list was composed specifically to justify the iMac pro's price.

Here's a much more reasonable list: https://pcpartpicker.com/user/xanderstrike/saved/mNDWXL