It's standard drug pricing. The cost of a patented drug are often not determined by how much it costs to develop or manufacture, it's how much people can pay vs. how necessary it is. Life saving drugs are the big ticket items because presumably you will pay anything you can to continue living.

It's one of the reasons I lost interest in pharmacology, it's really scummy. $3g isn't even the worst of it, some cancer meds -- at least last I was aware of it -- cost $10s of thousands a month.

Also, pharmaceutical companies R&D costs are eclipsed by their advertising budgets. They spend more money on ads than actually developing drugs.