Those big farms are likely running at a loss right now, considering the need to continually upgrade their hashing power. Cheap power cost does not solve this major problem of Bitcoin ASIC mining.

But even if miners are better off in the long run simply buying and holding bitcoin, they are still better off mining compared to conventional business investment because the next bubble will vastly increase the value of any coins they have not yet exchanged, thus ensuring that if they can hold on, they will prosper. I understand for example that the operator of the US Washington State bitcoin ASIC farm has a personal holding of over 1000 BTC.