Seriously, who needs all this horsepower? This isn't targeted at a home user, that's for sure. How many of these do they expect to sell?
It's a market that is actually quite large. . . and they will sell a lot. It's for the professional videographer, artists, movie makers... especially editors, animation studios, etc. What is great about it is that it has a 5K screen which allows you to edit a 4K video on screen with your CLIPS and your tool kit on screen with your 4K full frame video fully displayed. 4K monitors can't do that and at best emulate the actual image or overlay the tools and clips or have to have the tools on a second monitor, interrupting the flow of creation by separating the work from the tools. There are very few 5K monitor systems available that can do this. . . and they've been wanting an iMac that has the power to do the real-time editing with the monitor the 27" iMac has had for some time. This is it, an iMac with a workstation class computer in it.
It was only a couple of years ago that they were paying $5,000 for just the 5K monitors. Even a used Dell 5K monitor is $1400 these days.