The actual cost varies necessarily due to a number of factors. It's actual cost is subjective as it is interminably subject to change as a result of aforementioned factors.
Electricity is free in some parts of Africa. Liquid nitrogen cooling techniques compounded by walls of ice miles deep in northern and southern poles are not open to anyone, much less blogged about conclusively. The best mining equipment will be open source public discourse eventually, maybe. . . But that is not the case today.
^^^if you have ever looked at the A. S. I. C. Mining manufacturing concerns, you will see a profoundly disturbing justification for the above skepticism; they all "pretest" their machines for months beyond their "preorder" slated release date. Preposterous, that the pre-orders be postdated months after the promise, and even then, just a few lucky would-be miners actually receive equipment as advertised. (see Butterfly labs)
When the terrible miners finally rolled their first batch out, they could only be overclocked by the best in the world to put up 1.6Ths. (seen Teraminer)
(see what I mean)
3Questions that ask for current prices, etc, are off topic here. Answers would necessarily become obsolete immediately, and the purpose of Stack Exchange is to collect questions and answers of lasting value to future users. I have voted to close this. There have been past questions about the factors that generally affect the cost of mining, so a search could be helpful. – Nate Eldredge – 2014-08-16T00:49:24.473