Of course addicts enjoy being high. I'd wager essentially all addicts enjoy the high, even if the joy is just the abatement of withdrawal symptoms.
And while some addicts don't want to "quit", that's true, a vanishingly small percentage enjoy being addicted. In my reading and limited first-hand discussions, even those addicts who don't want to quit still wish they could "cut back", e.g., wish they could just be a social drinker or only shoot heroin on the weekends. They hate the powerlessness they feel, hate the control the substance has over their lives.
Lastly, I don't have hard evidence to back this up, but I've never read/heard an addict cite the high price of their drug being the biggest reason to quit. The biggest reason they want to quit is typically either its impact on their health or its impact on their relationships (or career, which is basically a relationship). I'm not saying you're irrefutably wrong about this; it just doesn't match my anecdotal experiences.
The one thing all addicts share is an expert ability to obtain and use their substance. If it is physically possible to get their fix, they will find a way. Also, illegal drugs are often cheaper than legal ones, because regulatory compliance and taxes add more expense than operating in a black market. At least, that's the evidence coming out of states and countries that have recently legalized certain drugs.
Legal morphine is already extremely affordable, about $1/gram.
On the one hand, I believe an addict will find a way to get their drug if they really want. On the other, a huge part of beating the addiction and maintaining it is to avoid situations where you know you'll be tempted to relapse.
As a personal example, I've struggled with cigarette smoking at times in my life, and it is undeniably harder (for me) to stay on the wagon when I can pick up tobacco on almost any corner, any gas station, convenience store, most pharmacies and grocers, etc. It's just everywhere.
Anyway, I'm just saying that I agree with most of that point – despite my being generally pro-legalization, pro-treatment vs incarceration. Honestly, if we as a society get to the point where an adult can pick up a bump of cocaine at every gas station, I think that will be a bad outcome. Accessibility doesn't necessarily mean prevalent and socially encouraged/acceptable, but it certainly could head us down that road – which is dangerous, at least for opiates/opioids.
And you make a good point about morphine. I guess it's because morphine's considered medicine and not a "decriminalized/legalized recreational drug", which are being subjected to higher "sin taxes".
Implicit in proper pricing is that it'd be legal and easy to use.
Which issues are you thinking about?
>opiates have little side effects outside of respiration depression and constipation
Maybe with proper dosage and medical supervision, maybe. But I think the biggest side effects of regular opiate abuse are addiction and a loss of productivity. I don't think those effects can be discounted. The biggest "waking" factor I have heard ex-junkies state as why they wanted to sober up were "I was killing my family", "I was killing myself", and "it was only a matter of time before it killed me or I killed someone for it".
That said, clean equipment certainly helps solve some of the issues, as infections are extremely common with intravenous users.
>I killed someone for it
I can't see how this is anything but a pricing/accessibility issue. Otherwise there's just no incentive -- it's about as expensive a habit as alcohol if bought legally.