The hell guys...
I had to stop mining when it dropped under 15 USD...
You guys have free electricity or what? :S
No one has free electricity. It's 'free' to the user but someone, somewhere pays. If it's a flat fee or part of a rental agreement it'll get reset when someone notices thousands of extra kilowatt hours being consumed.
My magic number is $9. Anything under that means it's not profitable to mine (high power costs, 6 series cards instead of 5 (not available for 6+ months here), currency conversion costs, very weak US dollar, etc).