>That's a silly claim unless you tax them to such an extent that black marker drugs become more competitive.

Not at all. First off, all the money we spend on the dea and other drug enforcement could be instantly recouped. Billions for those d.a.r.e clowns ALONE. Plus, I'd wager to say cost of legal production would be a lot lower than illegal production + illicit shipment to end users. That leaves plenty of room to make a decent buck on taxes. But yeah a big portion of money would come from all the idiotic shit we no longer would have to do with drugs legal.