Yeah if that's some Chinese chips they're garbage and not more efficient than HID. You can build that 8 x cxb3070 on 2 x hlg185 36A I mentioned and get 65k lumens directed at the canopy for 400w. Comparable to a 90,000lmn 600w HPS(reflector loss, and Cree 3500k/4000k have a slightly better spectrum), should be right at $400 and you just need heatsink to mount em on.
An HPS setup will run you at least $200, and a $50+ bulb every 6 months, and 50% more electrical usage. 200w extra @ 18/6 is $13 more a month, so that Cree setup would pay for itself over HPS in under a year.
315cmh is pricey compared to diy cobs, but not a bad way to go. Comparable to 400-450w of hps.