You're looking at things the wrong way.
First of all, there is no way to estimate how much weed you can per plant.
There are too many variables like: How many are males? How many were eaten by deer, infested with insects, how many had stunted growth due to improper water/nutes. how many were stolen, how many were seized, and on and on.
It also depends on the strain and the weather.
The way to go about it is to figure how many plants you have space for, how many can you take care of?
Prep the site, use heathy seeds/clones, use quality potting soil and nutrients, adequate water, and hope you don't get a bad strorm or early frost.
The best estimate I can give you is between none and 1 lb. of bud per plant.
Strain, size, age of plant, feeding/watering, soil, waether, insects ect. and lighting all play a vital roll in plant health & yeild. If you grow larger plants of a quality strain that yeilds well and was vegged for a good amount of time w/ propper feeding ect. you can get 1 lbs and more off each plant easy.