It's certainly true that drugs could be much cheaper if they were legalised. The black market has a hefty profit margin.
The idea that this higher price leads to more crime amongst desperate addicts is certainly the conventional wisdom, and you are in good company by thinking that.
However, one group of people who would disagree with you are the police. I think they probably have a lot of experience dealing with people who are both petty criminals and smackheads, so it's interesting that they perceive the causal relationship as being the other way around. They take a holistic view of the problem. Laziness and dishonesty are the cause. Stealing and heroin use are just symptoms. I think there is a lot of merit in this perspective, because people need to be responsible for the poor choices that they make. Especially if drugs are legalised.
Shareholders in the securities industry are having their worst year since 2002, losing $74 billion of their equity. That won't prevent Wall Street from paying record bonuses, totaling almost $38 billion.
Established technology tends to persist in the face of new technology. -- G. Blaauw, one of the designers of System 360