It's a matter of market clearing prices. A gross oversimplification, but $4 is the price the market can bear. Charging $5 in the developing world isn't much dif

It's a matter of market clearing prices. A gross oversimplification, but $4 is the price the market can bear. Charging $5 in the developing world isn't much different than charging $500—they just won't sell. Arbitrage is attempted, but the FDA is pretty good about stopping imports at port. Also, the primary distribution channels are fastidious about not taking goods from other locales so the market is grey/black and not worth the effort in most cases. The people who would buy drugs from India are probably using means-tested assistance programs and can't pay the huge sums insurers can.