What others said. There's another possibility here too: mine at a loss now, then hold onto the BTC, in hope that BTC goes up in value. If you mine $10 worth of BTC a day, but it costs you $20 to do so, that's not a loss if a week from now the value goes up 4x.

Not saying that's what they are doing, but it is not unlikely that huge mining operations know more than the public about what might happing going forward.