By cheap they are referring to how much YOU the miner are charged for that power. It has nothing to do with how cheap it is to produce. If you are producing your own power and it was sufficient then this would not be an issue. Yet, likely you like most of us have to purchase your power somewhere. If you get a DEAL on the price like Dan indicated in the article you end up dominating due to it being more profitable as you can run massive equipment that outperforms everyone else, and the cost to do so is less than it would be for other people if they were to try to buy that same amount of power/energy/electricity.