Those O.Pen cartridges are extremely expensive: $30 for 0.25g oil + 0.25g PEG400.
They come in limited varieties. I would consider you lucky if a strain offered adequately relieved your symptoms. I am not so lucky, and would need to vape alot of the "wrong" strain to be satisfied. That compounds the price problem quick.
My situation mirrors yours: Tolerant chronic user who want to get meds at a dispensary rather than grow my own.
Don't worry, there is a happy ending to this. I'm plenty medicated all day long on a fairly modest budget. You will have to roll up your sleeves and put in some elbow grease, but you would never smell anything cannabis-like in my house.
Where I live, the demand is highest for cosmetically perfect flowers as well as wax. Ice water extracts have fallen out of favor, making them very affordable. I also have access to dispensaries that lab test EVERYTHING[1], you may not be so lucky. Some places lab test just their top shelf stuff.
It is very easy to make an alcohol extract from hash. I use isopropyl alcohol, but I would use Everclear 190 if I could get it. There is definitely some finesse and technique needed with quickwashing flowers[2], but with hash it is child's play [3].
$100 buys me ten grams of 40% THC hash. I do not have the tools to measure my actual recovery rate, so let's pretend my wash is a 75% efficient conversion. I end up with 3g of THC as well as a bunch of terpenes that I swear have therapeutic effects. I'll round up the price of alcohol to $1 per shotglass-full (don't drink it).
PEG400 is
http://www.medical-and-lab-supplies...ycol-400-usp/polyethylene-glycol-400-usp.html ten cents per mil, so I spend fifty cents a batch. I myself dilute it further with PG ($4 bottle at CVS) but that is personal preference, I enjoy vaping, and I enjoy vaping PG.
I load it all up in a cobalt bottle with a eyeglass dropper, they are $1.50/ea from good nicotine-juice vendors. Finally, I minimize my long term costs by investing in quality e-cig hardware. Leaky non-servicable carts cost a lot in the long run.
So, that's me. $101.50 gets me the equivalent of a DOZEN o.pen carts[4]. I have control over strain, solvent, diluent, and sterility of mixing equipment.
[1]
http://www.magnoliaoakland.org/menu#hash
[2] alcohols are aggressive polar solvents that tend to strip flowers of chlorophyll and plant waxes, in addition to cannabinoids. If you screw it up you get unvapeable green dragon.
[3] I don't let my children have access to my hash, alcohol, peg400, or thc-juice. I am convinced that kindergarteners can do this if guided. So can you.
[4] does not include the value of my time, nor the cost of the energy to evaporate the alcohol.