The incremental cost of producing all those free samples is a pittance compared to the profit generated by your typical blockbuster prescription drug. Don't think of pharmaceuticals like a manufactured product like a car, where there's a cost of raw materials plus production plus a percentage for profit. Think of pharmaceuticals more like intellectual property, like software. Once you've paid a bunch of people to develop a computer program, there isn't much difference between making 1,000 copies or a million copies.

Generics are a different situation, but physicians aren't generally given tons of free samples of generics.