The actual colour/color of this iMac is Space Grey. The Space Grey Keyboard, magic mouse and trackpad come ONLY exclusively with this iMac. You cannot buy it separately. (unless you buy it from third party)
Sourcehttps://www.theverge.com/2017/6/5/15...lors-wwdc-2017
Prices will vary, as you can pick from the most high-end iMac to the baseline, but the baseline will cost around $4999. The high-end will probably cost $10,000 to $15,000.
Edit: The modular option of iMac Pro is coming out next year, which will give you options to upgrade everything probably.
I wonder if people will spend that much on a computer. My max budget was always $2000-2500. Personally, I own an iMac 5k 2015 highend and its very good that will probably last me 5+years, without worrying that its slow etc.
Lets not bash Apple here, but would you spend that much on a computer in general? Forget Apple Vs PC, just in general, would you spend 5k+ on a PC/iMac.
Official Specs https://www.apple.com/imac-pro/specs/