No, because that's an unstable equilibrium. If you are company B, you know you can steal 100% of the business by finding a cure.
Do you have examples of situations where cures have been suppressed in favor of expensive long-term treatments? Especially in a competitive environment, where there were multiple players offering competing long-term treatments that were both aware of cures?
Preferably this would be something supported by leaked or court documents, but independent investigations would also be interesting. I understand this is a high burden of proof, but everything I've seen seems to indicate that this is an urban myth. I certainly couldn't find any specific cases in a cursory search.
All else equal, people should be willing to pay a bit more (in terms of lifetime cost) for a cure than a treatment (certainty, finality premium). If that is the case, then cures are always at least equally worth developing. If that's not the case however, then yes we do indeed run into a bad local minima.
This certainly isn't true in social games. If anything it's the opposite - players will commonly pay more in subscription fees than they would for a total one time unlock of everything, since the immediate short term payment is less.