$21,325: Dream Machine 2015, dead tree Maximum PC magazine Oct. 2015 [View all]
CPU = Intel Core i7-5960X = $1,050
Motherboard = Asus Rampage V Extreme = $470
RAM = 64 GB DDR4 Corsair Dominator = $1,495
GPU = 4x EVGA GeForce TitanX Hydro Copper = $5,200
SSD = 4x Samsung 850 PRO 1 Terabyte = $2,560
HDD = 4x WD Black 6 Terabytes = $1,200
Cooling = EKWB custom-loop cooling = $450
Case = CaseLabs Magnum SMA8 = $520
Case Paintjob = Smooth Creations = $800
OS = Windows 8.1 = $100
Monitor = 27 inch 5K Dell Ultrasharp UP2715K = $2500
Mouse = Logitech Daedalus Apex = $70
Keyboard = Razer Blackwidow Chroma = $170
Headset = Kingston HyperX Cloud II = $100
Speakers = Adam Audio 5.1 System = $3,700
Sound System = Sound Blaster X7 = $400
LED Strips = Logisys RGB LED = $90
PSU = EVGA SuperNova 1600 = $450
They do this every year to demonstrate the theoretical limit of consumer-grade computing power. Of course it's ridiculous overkill but to people like me, it's interesting to read. YMMV. It's also going to be outdated within a few years, as always.