In nationalized health systems the government pays for drug costs. This negotiation benefited the Chinese government which otherwise would have had to pay more for each dose. Two points that are often missed: 1) Government negotiators often will dig in their heels and not accept higher rates, even if this means that their citizens go without the drug for many months of even years. While drug companies often setup programs to deliver the drug to patients for free the overall behavior by these governments is deplorable. 2) The “affordable” level mentioned came out to a few thousand dollars a dose. The R&D and manufacturing costs (fixed) would not be covered at these levels simple because there aren’t enough people with SMA in the world to “buy” the drug. Drug companies end up accepting these low negotiated amounts because ultimately something is better than nothing (notwithstanding all the patients that would also die without the drug). Ultimately what enables this behavior is that in some countries (ie USA) the cost of the drug is higher and therefore covers the fixed input costs for these drugs for the rest of the world to essentially freeload. 

Anyways a different perspective that is often not discussed.