The guy sounds like a moron.
I tested cex.io for a week with 1.5 btc and left with 2.2.
Pretty decent return, just didn't have the time to invest, even if you just bought GHs, it's normally cheaper than buying the hardware and you get the same results... plus you can resell it easily.. (While everyone is waiting for things to ship and then the hardware you have becoming useless.)