I read somewhere that the second most valuble crop grown in the US is marijuana.
Only corn generates more cash.

My guess is that once most of the states legalize pot and farmers start growing acres and acres of it then the prices will drop dramatically. Why should pot cost more than tobacco. My mother was from Georgia and no one went into fields and stole tobacco.

The main reason it will stay high is because of the taxes. States will jump at the opportunity to tax the hell out of it. But if growers are thinking that they will be able to grow pot and sell it for $200 an ounce those days are over.