The so-called 'Holy Grail' of growing is 0.5 grams per watt per month, or 1.0 grams per watt per crop. Some people even exceed this (search for Tranoble's sealed room thread for an example), but it's rare. So, theoretically you could yield 400 grams, if everything goes right and conditions are optimal. In practice, aim for half of that, be happy if you achieve that, and consider anything beyond that a bonus. That way, if you don't hit the holy grail (I never have), then you won't be as apt to be disappointed.

And obviously, yield depends on a lot more than just the lighting. Ventilation, temps, grow medium, nutrients, strain, number of plants, veg time, how they are trained and grown, pot size, humidity, pest problems (or lack of same), and so on, they all influence yield to one degree or another.