I don't think the economics are comparable at all. Given that cannabis is literally an invasive weed, getting started is really easy and takes very little (horizontal) space. A past neighbor in Northern California just randomly stuck a few seeds from a dispensary in the middle of her backyard garden, did a little research on how to take care of it, and four months later had more cannabis than the entire block could smoke before the next harvest was ready.

A single tobacco plant won't yield much more than 2 ounces and that would last a pack-a-day smoker less than a week, saving them about $40 (not including labor of actually making the class A cigarettes). 2 ounces for a single cannabis plant is a relatively poor yield but would still last an 8th-a-day smoker 2 weeks and save them at least $400 and there is up to a 10x difference between a poor yield and an excellent yield. The reward/effort ratio for these two plants is worlds apart so I don't think the comparison to tobacco is particularly helpful.