One model is that a government pays a license fee that allows them to produce the drug in unlimited quantities for their country. (In practice, they could buy the drug from the manufacturer at the marginal cost, or they could use another pharmaceutical company as a subcontractor.) Sometimes there is a deal, and the country may get orders of magnitude higher health benefits for a marginally higher price. And sometimes the company refuses, because the deal would interfere with their business model in other countries.