the players can already satisfy and profit from 50% of the market with their existing product. Anything they pay for new product will only benefit them some portion beyond the first 50%.
There's this thing called competition!
If a single player had monopoly control of the market, then sure there'd be no reason for them to push a new product. (Especially as the product is likely to _decrease_ the overall size of the market if it reduces the time patients are under treatment.)
But in real life there are multiple companies competing for a share of the market. If one of them can offer a product that demonstrates - and the FDA or MAA accepts as having - better efficacy, then they might be able to double or triple their sales.
TIS Price at posting:
53.0¢ Sentiment: LT Buy Disclosure: Held