no1 has an answer?, that's a big bag of dicks.
All I have is questions....
do you even know how many lights?
what kind of grow/medium/container?
what kind of experience do you have?
what genetics are you running?
how long you gonna veg them for?
what style of grow are you gonna do?
are you using co2?
If you have skills and the killer genetics (low yeilding high $$$ cuts like OG, Bubba...) you can pull 1-2lbs per 1k.
If you don't have skills ands your runing the killer genes, you'll be lucky to get 1/2lb per light. Very lucky....
If you have skills and are running B grade genes (high yeilding pretty looking midgrade like AK47, Big Bud...) you will get 2-3lbs per light.
If you don't have skills and are running B grade genetics you will get 3/4-1lb per light.... maybe.
If you want to light up a room and max it out, unless you feel like wasting money you better know what the heck you are doing.
Not trying to be a dick but from the vagueness of your question I am under the impression you don't have many grows over 2 plants under your belt, if that.... otherwise you would have divulged a bit more info to allow a proper guestimation. its your money do with it what you will...