I agree with most the thread on ads. Manipulation markets for mind altering substances sounds and are dystopian to me.

Taxes should be normal rate for goods and services + the public cost to research harmful effects + cost to migate/solve harmful effects.

If that industry leads to children being abanded by or essetially abanded by their parents then the cost to raise and care for those kids and help them navigate that trauma needs to be reapplied back to that industry. Both income and sales taxes should be applied as needed (for example if research suggested a higher sales tax would just be circumvented by black markets).