Try a web search for the most profitable drugs in pharma. They're not one-off cures. They're drugs the same patient takes repeatedly for decades: insulin, statins, pain-killers, etc.

That's not the only factor, though. If someone else is avoiding selling a cure to do something more profitable, you can compete with them by selling the cure and still make enough.

There simply isn't a "cure for pain" to replace painkillers, but statins and co could be avoided if we taught people actual good diet advice.

The worst problem with statins is the personality changes: https://www.bbc.com/future/article/20200108-the-medications-... …which doctors wouldn't admit existed because they aren't taught that "evidence of absence is not absence of evidence".