Then why do those who argue for a war on drugs not argue for that war to extend to alcohol, caffeine, and tobacco? If it is indeed a war on drug abuse, then where are the calls to incarcerate those who abuse alcohol in combination with prescription drugs (by the goverment's figures, that includes about 1 in 6 Americans over the age of 60)?
This is a war on drug abuse. Proportionality has nothing to do with it, and expense is not an issue. It is a question of values - you are either for it or against it.
There are a whole bunch of wealthy, well connected people down at the Betty Ford Clinic being treated for alcohol and prescription drug addiction. By your reconing, either all of these people need to be locked up for drug abuse, or their doctors do for fraud for treating them for a non-existing condition. Which is it?