>>1 Depends on what you plan to do with such a beast. If you plan to game on high settings across all monitors (assuming this is even possible at such rediculous resolutions), you're probably looking at in excess of $10k worth of hardware. $3600 of which is just for 24x 1080p monitors. $4000 for 4x flagship-level graphics cards in tandem (GTX Titans, SLI).
If you want a workstation that's as good at CAD as possible, even more because Professional graphics cards are more expensive than gaming ones, and Xeons are more expensive than i7s.
If you just want to browse the web in a rediculously awesome way, then you could probably drop the cost by a few thousand dollars.
Please, build this and upload the pictures in all of their glory.