How many ounce will you get of 4 weed plants?

It all depends on how fertilized the plant is and how ideal growing conditions are. Trying to grow buds turns very sour if you don't have the right temperature, moisture, light, etc. There are also many additives you can put in the soil to get the most out of your gardening. I really can't accurately give you any kind of number because I don't know how well these babies are treated.