Big Pharma would not be spending hundreds of millions of dollars to build out their sales and marketing infrastructures throughout China, including the interior portions of the country
That's not the way I understand it. China's drug prices are government controlled and normally set at domestic cost plus 5%. Then there is an additional 12%-15% added for the distribution channel. If a drug is then used heavily, the price is cut by the government.
The western companies see their largest benefit from what research, trials or API they can export from China for use in their other facilities or markets.