Could create it and make a profit selling it.
If the cure generates less profit than current treatment, and if you’re currently selling treatment, then that’s not going to be worth it for you.
If you don’t, well you still need to get it to market, which requires substantial investment.
My point is that the described scenario is not entirely unlikely. For example, type 1 diabetics in the US need something like $600 worth of insulin, every single month for the rest of their lives. Say that’s 60 years, you’re looking at $430k, not even counting needles, sensors, and other stuff they might need (or absolutely need). Average patients won’t be able to cough up nearly as much for a cure.
Pharma has just been way faster than tech in realizing that the subscription model has far better yields.