I get what you are saying about the percentages and how it will skew when dealing with smaller components. I was also considering an hourly cost but I was not able to determine what that would include.
The customer is the son of a millionaire that I go to college with and he said that he wanted Intel's newest Broadwell-E CPU so I built the computer around that. He plans on using the computer for everyday tasks like searching the web, gaming in 4k on a single huge monitor AND gaming on 3 1080p monitors, and he also plans on using it as a workstation. Again he just wants the best of the best so he can brag to his friends in his home state. That is why it has 128 GB of Trident z 3200hz RAM, the SLI 1080's (would be quad if NVidia still supported it), and all the watercooling parts. The computer is fully planned out on paper so everything will fit and work in theory when the parts get to me.
I forgot to include the radiators in the parts list I linked. I am using a quad 120mm rad in the basement and a triple 120mm rad in the top. The monitors in the original link were also just ones thrown in there I put the correct ones that he told me he wanted in the new list. UPDATED LINK:
http://pcpartpicker.com/list/cfDLkT
Any suggestions are welcome for better parts and such. There is no price limit so he doesnt care about price per performance.
---- updated ----
And he will be reciving the Vive so it will be used for VR as well.