I regularly see (and buy) “96-120 cup” cans of coffee for around 5 bucks, maybe $9.49 or so at notoriously high-priced stores. Not saying it’s the best, but typical mass-market national brands (you can get store brands even cheaper and pretty sure "dollar stores: have a one-buck can that’s 30 or 40 cups). I use a couple a month.
Painkillers (Percocet/Vicodin) will cost around $1-3/mg of narcotic when bought “on the street”. Typical pills contain 5-10 mg. How much you’ll spend depends on what you’d consider a “moderate” addiction.
As someone with long term chronic pain I’ve been on prescribed “maintenance doses” of 2-4 pills of 5-10 mg per day in the past. This would just take the edge off the pain enough for me to function better. I no longer get or take them but my insurance co-pay was $5/month. I was never addicted and stopped taking them with no ill effect other than fully suffering the pain.
Most pill users wouldn’t be “addicts” at the low end, but might be dependent.
Recreational use might be $10-20 for once a weekend use (with prices on the low end of what Ryan mentioned).
I knew someone that was spending $200 at a time to get high. She would go into withdrawal in about six hours if she didn’t have another “dose” (although she didn’t need the full amount to keep the withdrawal away, but it wouldn’t get her high). She was kinda at the high end [when I was with her at the hospital the doctor asked me how much she took - I told her and she thought she heard me wrong or that I didn’t know how to do the math] - as I knew she had taken over $600 a days worth. I know people in between.
Most pill “addicts” (if we are using you “will go into withdrawal without it” as a measure of addiction) - will be taking at least $10 worth 3 x a day.
Most things are harmless. It’s only a problem to be addicted to something if the thing to which you’re addicted is illegal. Then the cost is that of the black market price increase, the risk of legal problems, the risk of adulterated substances (black market again), and risk of unknown quantities/purities (black market again).
This is why everything should be legal, but that’s another subject.
Ever heard of alcoholism?
Or lung cancer?
Well, I’ve heard of Al Capone…
What about hookers? The very name implies that prostitutes are addictive.
The cost of hookers depends, of course, on both quality and location.
They cost about $300/shag in a major American city for someone attractive enough to be, uh, worth paying for it. The ones who cost $100-$200 are significantly less attractive.
In a foreign country, well, I’ve heard they can cost from about $60 U.S. per shag in certain clubs in Germany, to about $80 US in Argentina, similar prices in most of Eastern Europe. (sort of amusing that paying for sex is actually a fairly consistent price assuming a woman of roughly the same attractiveness).
I’ve heard that Thailand is the cheapest, but I don’t have direct pricing data.
What about usage rates? Well, from reading various accounts, I’ve heard that enjoying hookers can be quite exhausting and it is self-limiting. It probably depends on the gentlemen, I’ve heard of, uh, “usage” rates anywhere from 3 times a week to daily.
Nah. Cambodia, Laos, Myanmar … all cheaper there. Vietnam even. Seriously.
If you’re addicted to alcohol a still might not be a good idea; the wrong temperature and the outcome can be seriously dangerous. Even with the right temperature the outcome can be dangerous.
A better, (relatively) healthier option is brewing your own wine. After a small outlay it works out at $1 upwards per bottle, and the quality can be (subjectively) as good as shop bought, minus the chemicals allowing it to stay on the shelf for months or years.
A moderate addiction would be a bottle per day, so around $500/year.
I bought 1 kg of caffeine for $25 on eBay. That is equivalent to 10,000 cups of coffee, or 0.25 cents per “serving”. $0.25 worth would probably kill you.
What do you do with all that caffeine?
My husband and I spend £20 a week on Coke Zero.
I saw Ralphie May in concert a couple of years back (on April 20th, go figure). In honor of the date, a goodly bit of Ralphie’s act concerned his [former] weed habit.
Ralphie stated that, before he gave it up, at one point he was smoking five and a half ounces of weed per week! Assuming he was paying for (he likely wasn’t - he mentioned “heavy handshakes” from fans) primo weed (say, $500 per ounce), that’s $2750 per week.
Similarly, I’ve read that Snoop Dogg smokes upwards of 80 blunts per day. No idea what a blunt costs. But, still. Dayum.
*Everything *becomes an energy drink. 
Pretty much! I actually haven’t used it for much yet, but the idea was to make caffeinated smoothies, etc.