The article is all about the cost of the hardware, neglecting the more significant cost: electricity.
Once you're above baseline power of 11 kWh/day (as any geek is), Southern California utilities get about $0.13/kwh marginal, with taxes, distribution, etc.
The 24-core beast built in the article probably draws some serious current. Hard to guess how much, but I'd guess about 500W? Anyone know?
The 24-core beast will draw a minimum of 380W (using the power supply calculator:
http://educations.newegg.com/tool/psucalc/index.html)