The 1000W DE bulb is ~40.5% efficient from 400-700nm, when brand new. That number is important to know, but it does not allow us to compare directly with the LED efficiency numbers because it is before reflector/glass losses, different spectrum and does not account for uniformity/spread.
If you believe
these numbers from Growershouse, there is a lot of weakness from the Gavita reflector compared to the AC/DE reflector. If so, you need a $300 reflector to optimize the 1000W DE. That really changes the picture regarding up front cost comparison with LED.
Taking into account electrical savings from the lamp itself, electrical savings from the hood ventilation and tent ventilation, electrical savings from air conditioning, bulb and reflector replacement costs. Long runs of air tubing is expensive, loud, annoying and takes up working space. Constant heat plume blowing out of your grow op affects security?
On top of all that the COBs can put more light down than the HPS so you could increase your yield and maintain it for years. It is hard to put a price on that, rent/mortgage/taxes are expensive for most of us so space is very expensive.
One more for good measure, cooler canopy temps = faster finish and more frosting/flavor/potency and that is the end goal for most.