LSD would be even cheaper. Just a single 25kg yield could supply one hundred million doses.
In fact most street drugs given proper manufacturing could be just as cheap, if not cheaper than weed.
Shit LSD is easy, MDMA industrially produced would be just as cheap. Don't need to farm, cultivate, harvest and prep most chemical drugs. In fact pretty much all street drugs could be mass produced with ease ... marijuana however has significant hurdles ... you know waiting for it to grow ...
Hence this 'yeah man weeds so cheap is should be legal' is probably the most ridiculous argument I have ever heard in respect to the legalization of marijuana.
Lets not even touch on what would happen to society if they made weed free. Sure crime, depression and boredom would drop. But so would social advance, society and human progress. Yeah that's right, weed generally makes people dull, boring and kills their drive and ambition.
There's a reason all the stoners I knew at uni were retaking years. One a doctor, dropped out, studied tissue engineering, ended up with a bachelors. Computer Scientist, retaking his 3rd year. Dropped out. Wanna be dentist, tried applying for dentistry for 3 years in a row, never got it. Chemist, took 5 years to fail his 2nd year and drop out. Japan students numerous japan students. All failed. All dropped into East Asian Studies, the Japanese reject list. Some lasted it out, most didn't. There's a reason all the stoners I knew generally failed. They were decent guys, it's just their habit killed any push and ambition inside them. They could of all been 5 times what they are now. But they preferred to spend their weekends and evenings getting high.
Weed for them was almost as cheap as Alcohol. For them it wasn't much of a choice, but it was still one they made. Now your telling me you want to hand joints out to them for free? Yeah no. Make it legal. But free? No. That'll screw up so many people.