I could see how this would work, but would the following scenario seem so unlikely:

With pot being legal and regulated, the price would drop severely, and the weed sold at a Walgreens or whatever would be top-of-the-line, expert-grown cannabis that you'd be able to afford quite easily and at any time you choose. Growing is a process, requires money and time-- you could just drop the $40 and get an ounce of crazy weed.