While I agree that the US could learn a lot from India's billion-payer system, the big drivers in cost differences wouldn't apply.
India's system is cheaper specifically because it doesn't have the complexity of the billing system that the US has (and, for that matter, European countries as well). But in addition, India explicitly does not recognize a wide range of drug patents that the US does. By paying more for prescription medication, the US market funds a huge amount of medical research (50% of the medical research in the entire world) which countries like India are able to access essentially for free.