Not nationwide, 30$ an 8th for hemp in most places, some places charge 250$ for the real stuff. It is cheap in certain places, you're right, more expensive growing unless you do it from scratch..
I bought weed at Christmas and they gave me 2 and a half ounces and a 1 gram 'pre-roll' for $25. It was so cheap I questioned the price and they thought I was complaining and yelled at me. He said "What do you want? I just gave you two and a half ounces for twenty five bucks, Bro!".