Even if it was not explicitly approved as a drug, if someone was allowed to grow the plant for their own consumption and found it provided adequate relief of symptoms for $10/month, why should they not be allowed to use the $290/month could save for whatever other purpose they see fit?
I would suggest they take that $290/month and put it in a savings account. One day they're going to need it to pay for a lawyer to get their sorry ass out of jail for growing marijuana.