Ethics of drug dealing

First, some premises:

• Cocaine, heroin, methamphetamine, and their ilk (henceforth "drugs") cause direct harm to people who use them.
• Drug use comes with less direct harm to other people, from an addicted drug user's struggle to get more.
• Drugs are addictive, and so have price elasticity of demand near zero.
• There are already many people addicted to drugs, and many people producing drugs to sell to them.

By offering to produce a good, you shift the supply curve right, however slightly. This decreases price and increases amount sold. More of the change is in amount sold when the good is more elastic.

From the low elasticity of drugs, we conclude that making and selling drugs, economically, serves mainly to decrease their price. If drugs are cheaper, then people addicted thereto struggle less to get more, and so cause less harm to others in their struggle. For especially addictive drugs, making more for the market is an ethical net positive.

This contradicts intuition. Part of the difference lies in what you would do when producing drugs. I assumed above that, as a new drug dealer, you only affect the supply curve. If pursuing profit, you may try to sell more by shifting demand by getting more people addicted. That would be harmful, arguably evil. If your only customers shall be people already addicted, who just left or lost their previous dealer, the argument above holds.

That is, leading more people to use drugs is wrong, but one can make and sell drugs while the population using drugs stays the same. The other caveat arises iff drug dealing is rare, in which case becoming a dealer may lead addicted people to get drugs when, previously and otherwise, they would have gone without.

All that was consequentialist. Naive deontology would also approve of simple drug dealing: it can be done as a normal, consensual transaction, causing harm only from how the customer uses the drug after buying it. While it would be rare, for all you know, the customer could be throwing the drugs they buy in the ocean, rather than harming themself or anyone else.

However, even if selling drugs is ethically neutral to positive, there are other activities, also of significant profit, and with far more social benefit.