Depends on the strain and such, if you have a fast growing strain, possible 1-3 oz. If your real good at growing and you know all the tactics and stuff you can get possible 4+ oz. Maybe in the small chance you could get 1lbs.
EDIT:
Here are some of the things to consider, your lights, nutes, strain, your skill, how sterile your room or location of growing is, there are so many.
It could all be destroyed by mites, disease, severe nute burn ETC.
Best thing to do is to just keep your tools clean and water as necessary, give nutes in correct proportion, good lighting etc.
Just read threads about massive harvest, and they usually tell you how much each plant yielded.