What to expect from (2) 750W HPS?

I bought (2) 750w Lumatek HPS for 50$ bought some Plantmax bulb also. I think about using them at the same time for 8plant (Northen light) clone, vegged under 1000W MH for 2month. What should i expect from 2x 750w?

Thanks

I've seen 2Lbs, 2.2lbs with 2x 1000watt...

anywhere from .5gram/watt for a noob to 1gram/watt for a good grower... you could get 750-1500grams.. anything less than 750 means you did something wrong or are using a low yielding strain