Which is why nobody's addicted to crack and there's no problem! /s

The notion that people are perfectly free and rational entities is a dangerous fallacy. People don't have perfect information, they don't make perfect decisions, and if there's something the government can do that improves the lives of many while inconveniencing few, then it's absolutely the government's job.

There exist substances which will get you addicted instantly. Do these have any place in a free market? Where does the rational "value equation" come in to that?

The problem with crack isn't the cocaine it's the format. Crack is the chemical equivalent of a freemium game, no buy-in and once a user's involved they only pay a few bucks for each subsequent hit. A few dollars quickly adds up to much more than that same person would have spent on an entire 8ball if they were capable of delaying gratification, but they aren't. Console-type games that you pay more for and only pay for once are the digital 8ball to freemium's digital crack rock, addictive but not nearly as destructive.

Perfect Information is what the government needs to guarantee and regulate, not morality. Apps need to be transparent and honest and substances need accurate labeling and purity from contaminants. Heroin is a one-way ticket to pain and degeneracy and everyone in the Western world knows this; it's a terrible value that generally only appeals to someone who's already hooked on opiates.