i understand what you're talking about romdog as i am a medical patient here in colorado and many times i find the medicine i'm paying 10-15 dollars/gram is lacking. i asked the owner and operator of our numero uno dispensery here what the deal was and he gave me a list of reasons.
1. different strains for different illnesses hense the detailed follow up from the dispensaries medical staff to see what works best and for who.
2. many dispensaries try to milk their medicine for all it's worth. meaning the herb you get in the end has been rolled on the keif screens to press pucks and then sell them for 30-70/gram keif depending on strain.
3. different growers = different potentcy of medicine. some dispensaries when starting out don't have a medicinal hook or if they know a few growers those growers might still be fine tuning their techniques.

as far as not getting the quality of medicine in cali my first response would be to of course grow you own, but that is not a realistic option for everyone so possibly talk to other patients via support group or the interweb. good luck with your quest...