that depends on your lighting, the nutrients you use, how you train your plant if you train at all.
There are so many variables that no one can answer you with any accuracy. I know some growers that never get more than a half ounce and others that can harvest a half pound( or damn close) off of one plant.
Genetics definatly play a role in the ammount you harvest but environment is just as important if not more important a factor.
I'm hoping to get 160g off my plant which will provide medication until my next harvest, anything above that and i'm giddy. My first harvest was a half ounce, my second was 3 ounces and i'm hoping for the mother load of sweet Blue Mystic for this harvest since I LST'd the hell out of the plant.