The UK taxed sugar (to try and curb soft drink consumption, thanks Jamie Oliver) and it just resulted in the non-diet/zero versions of everything containing both sugar AND sweetners. They managed to stay the same price and now all taste like shite, but I guess it's cheaper for the poor corporations who had to comply (by changing their drinks entirely rather than paying the tax).
But... most places have banned these drugs. I'm not following your logic. Are you saying they should be legal because we're free to ruin our health in other ways?
I'm an advocate of actual freedom and personal choice. Meth is obviously a downward spiral for most. However, the issue is most drugs don't start out that way. My point is that criminalizing drugs is the wrong approach. That is all.