50 watts per square foot is plenty (although a little more is always nice ). If you're flowering plants from seed, with minor training, you could expect circa .5g per watt, so 5000*.5 = 2500g = 5+ lbs. The yadda yadda yadda part of your post (the part about assuming that everything else is properly setup) is really the key variable left in the equation.

That weight would also be per flowering period, so if you rotate in a new crop every flowering cycle (7-10 weeks), that could be 4-5lbs every 2-2.5 months!!!

This is all generalization you realize, as there are too many variables to really say, so...

Good luck chief!