Well, it's certainly got most of them beat on price, at least if one can avoid paying a black-market premium.
If someone can get adequate relief from a product that costs them $10/month to grow, whereas using prescription medications sufficient for such relief costs $300/month, will you personally pay that person $290/month in exchange for not using the $10/month remedy? If not, what gives you the right to impose $290/month of extra expenses on that person?
Medical marijuana will never be approved in a smoked form, so get that idea out of your head. If anything, it will be available in a form and at a price comparable to other pain relieving drugs.