[cat199]

any specific food has a at least one if not many near perfect substitutes, whereas any specific drug likely does not.

validity of OP's conclusions aside, this is not apples to apples from an economic perspective.

see also:

https://en.wikipedia.org/wiki/Commodity

https://en.wikipedia.org/wiki/Fungibility

https://en.wikipedia.org/wiki/Substitute_good

https://en.wikipedia.org/wiki/Price_elasticity_of_supply

https://en.wikipedia.org/wiki/Price_elasticity_of_demand

etc.