According to
Goldman-Sachs curing diseases like Hepatitis C via one-shot cures is not a sustainable business model.
They state that Gilead Sciences (a company that produces Hep C cures) brought in 12.5 billion at first, but is expected to generate less than 4 billion now due to fewer people infected.
Goldman-Sachs suggests that companies focus on disease that are high occurrence to keep profits high.
Not surprising really. If you cure all those infected with a disease you aren't going to sell as many cures for it. But that doesn't mean stop focusing on them. No, instead just have realistic expectations of what will happen. Dispense the cure, end the disease but be ready to move to the next major disease to cure.