Well, is quite sure that prices at cex.io are in real bubble:
I used mining calculator at http://mining.thegenesisblock.com/ with buying 100GHS at current price from cex.io for 4BTC (1GHS=0.04BTC), and I couldn't break even with higher monthly increase of difficulty than 32% per month, see http://mining.thegenesisblock.com/a/7908fc0daa
If used more appropriate increase in difficulty of 100% per month, I can break even after 6 months when I buy 100GHS for 2BTC (1GHS=0.02BTC) and after next 6 month the profit will be 0.04 BTC, see http://mining.thegenesisblock.com/a/2be83da502

I guess that market participants at cex. io dont use math. Any comments?