I wouldn't be so sure as to not keep an eye on this and did u run co2 or even try it with less light I use 2 x600w in that size area with no ac which also churns up electric and no co2 depending on strain anywhere from 40 to 50 oz bone dry so I guess u can see where I'm going with this :)
And just incase u don't off that amount of juice I would have been pulling 9lb which is a 50% gain and that's with out the gadgets
3 a light is hard to pull consistently. I only count the rock hard buds, no larf here. Your average is 2-3lbs in a 4x8.... Mine is 6-8lb in a 4x8.... your electric bill is $150......my electric bill is $650..... But I have 3-5 more lbs than you. so if we do a cost per oz to grow, mine is vastly cheaper even paying more for electricity.
What gadgets do you speak of? DE bulbs? AC/DE hoods? The window AC I built a manifold for and piped into my tent for about $250?
Lastly I was running OG Kush which isn't exactly a great yielder, blue dream or gorilla glue would have yielded more. Sometimes I used to grow strains when I got a special request/offered more for knowing the plants yield less.
Nowadays I run little over 10k in a 20x40 greenhouse. That's flower only. It will average over 3 a light because the sun is my supplemental light lol. And I have room for trees.....