They would extract any part of the plant that has trichome glands on it. Thats where the cannaboids live. For extraction, we want a bushy strain that covers itself with dense trichomes. More leaf surface area means more trichome glands, which means more high-potent oil and that equates to more money.
Chemist72 has done some beginning analysis of cost per pound and came up with some crazy revenue numbers of 5 to 10 times the value of flower buds. We just need to confirm, but I believe they are in the ballpark.
News 
Market Data 
Discover 
