Let me start with what this article is not about. It's not about value. It's not about mainstream (or even enthusiast) gaming. It's not about comparing AMD and Nvidia.
Now that official support for three- and four-way SLI in games is gone, this article is about the pinnacle of performance achievable in late 2016 with Nvidia's Pascal architecture, assuming money is no object.
This article is also about tinkering with really high-end hardware, trying to overclock two Titan Xes in SLI, seeing how they fare in VR, and testing whether the lack of HBM2 (Nvidia opted for GDDR5X instead) is a big deal.