The lowest cost center for mining bitcoin is absolutely not China. The reason mining power is currently centered in China is because producing the latest-generation ASICs is cheapest and quickest in China and for various reasons the companies involved prefer to just bring them online in China quickly.
Soon ASICs will stabilize on the most modern production processes and commoditize and Bitcoin mining will shift to where the marginal cost of mining is low -- Iceland or other cold countries with extraordinarily cheap energy.