Though there is no evidence to support it, the prospect of incurred public healthcare costs subsequent to legalized drug access has granted an illusion of legitimacy to the prohibitionist argument. This presents challenges in advocating drug legalization from an economic standpoint. Much remaining support for current drug policy is premised on the assertion that society as a whole should rightfully pay for the healthcare of others (through a mandatory system of income taxes). Those who oppose drug law repeal on the basis of potential healthcare costs are perhaps presenting the only reasonable argument of all prohibition-advocates; but only when we uncritically accept the aforementioned principle of 'all for one, one for all' - wherein an individuals healthcare is paid for by others who may object to his high-risk lifestyle choices. A system built on such socialistic economic principles is irreconcilable with the traditional American ideals of individual liberty, personal accountability and self reliance; The very fact that such a system is so ingrained into our culture as to affect social policy illustrates the intricate web of socioeconomic factors which complicate & impede our ability to rationally approach the issue of drug law reform & repeal.
Let me spell it out:
When government or society grants rights to an individual, not only can it tell him how to exercise those rights, but it can also take away other rights.
For example: When government provides you with food on the taxpayer dime, the government and taxpayer can dictate your diet.
Or for instance: When one collects welfare or unemployment checks on the taxpayer dime, the government & taxpayer can then legitimately dictate one or more of several aspects of the recipient's personal life and lifestyle. The case could then very well be made for impeding his privacy by requiring random urine screening, or dictating everything from how many children he may raise to what type of car he can drive, where he can live to a whole lot more.
When government provides you with healthcare on the taxpayer dime, the government and the taxpayer at large can then dictate any health-related aspects of your lifestyle. The argument that "drug legalization might increase healthcare costs" (whether or not that's the case is a different discussion altogether) all of a sudden becomes relevant.
By dictating our personal responsibilities and individual duties to the social care of others, our freedom to make many choices is easily lost. This is just how the social contract works - fewer personal duties and responsibilities cost us our liberties in exchange.