That depends on so many variables it just isnt funny. An outdoor plant given the full season to grow with all the right fertilizers can yield in excess of 5 pounds.
An indoor plant under optimum conditions yields on average 1g per watt. That is if ur using a 400W light, then u should get 400Grams off ur plant.
Im not a big grower, so im happy if i pull a pound to a pound n a half off my 4 plants.. that does me just fine until my next harvest.
Wat r ur growing conditions like?