You don't have a yes/no payout. You have a graded payout. E.g. you might have a 1 shot cure pay out the full amount, but a sustained treatment only pay a smaller %. This lets you encourage development of the most effective treatment, not the most profitable. It's currently better to make a condition chronic, and so need treatment for a lifetime, than develop a cure.

You also don't pay out all at once. By spreading it out over sat 10 years. It means it can be adjusted if the company's claims are... less than accurate.