That's an excellent example of how even government provision of healthcare can be more or less regulated. The law doesn't allow the agency running Medicare to

That's an excellent example of how even government provision of healthcare can be more or less regulated. The law doesn't allow the agency running Medicare to not buy certain drugs which is the other side of the coin in terms of them not negotiating. By contrast the NIH is legally allowed not to buy a drug and uses that fact to negotiate lower prices.