How were you using the Specrum Kings? Did you have them at least 18 inches from the plant tops and reflective sides around them? I've seen several videos and forum threads where people did get a pound or close to it per light. There's nothing wrong with using LED high bay lights to grow plants. White LEDs do work for plant growth (see
article) and have a pretty good specrum for it if you look at the graphs. Here's the
graph. SK lights have the red line spectrum, I saw the meter readout under them and it matches exactly. They're running 4000k neutral whites. As you can see in the graph, they have more blue and red/far red than HPS. HPS light is 73% infrared, in other words heat. That's why it burns the fuk out the plants and heats the growing chamber up like a blowtorch. With the high bays, all the heat comes from the top of the fixture and is conducted away by the heatsink fins. If you put those fins outside the top of the chamber with the reflector part sealed inside the top you would have virtually no heat going into the chamber, no infrared light at all.
SK actually charges a reasonable price for their high bays, if you look on eBay or elsewhere. In Alibaba they look cheap but that's because you have to buy a crapload of them at once and you have to pay about $200 each for shipping from China. On AliExpress where they're sold in small amounts or singly, they're about the same price as SK with the shipping added on. If you can find another US source for Cree LED high bays with lower prices than SK then take it. I haven't found any. Those lights will work if you use them right. You could also use a different power supply to drive them at 1 amp and you'd get about twice the output with less than twice the reduction in efficiency (see
here). The heat would increase so you'd probably have to put a fan on the fins to cool it but it would work.
Now regarding the DIY lights that are supposedly better, how much does it cost to make them? How much trouble is it? Where do you get the LEDs and where are the test results showing that they work better than neutral white Crees? I haven't seen anything in this thread other than vague claims and unsupported assertions that Cree Led high bays don't work well for growing Cannabis. Lots of people say otherwise so the onus is on you to prove the contrary. They're definitely a whole lot brighter than red/blue type LED lamps and have a better spectrum. True that red and blue are a bit more efficient than whites, which are really just blues with added phosphors, but they don't put out anywhere near the total PPFD as the high bays. I saw the meter readings. You can see for yourself
here. Granted, the high PPFD readings are under the middle of the light but red/blue type lamps don't have that intensity anywhere. You could just use a light mover to move the light around.