well, Cobain didn't have an extra 20 years to blow all of his his money on heroin, which he most certainly would have done had he not killed himself in 94
Not sure your prediction of an alternative ending is accurate, but who knows. He did check himself into a clinic, but also checked himself out to soon. If Kurt did get clean, or semi-clean, he was pretty frugal with his money in the past.
He made Courtney return an expensive Lexus I believe, and he pretty much shopped at thrift stores. He drove a used Volvo. The one major purchase was a fancy home, but I don't think his life style would ever been over his income ever.
He fired a chef, because he made gourmet mac and cheese, not the cheap Kraft kind.
On the other hand, Scott Weiland was from California, and reports of him living a high standard life style, which is probably why he left so much debt.