Find me one LED seller that lists efficiency on their advertisement. Find me one. Remember, efficiency is a unitless number between 0-1. They feed you all sorts of other BS numbers.. sure.., but if most of them told you their efficiency, nobody would ever buy them, because gavita's efficiency makes almost everything look like a joke. 42% is very high. The people getting 50% efficiency with DIY are underdriving to extreme levels, and using top flux bins, which means huge startup cost.. Most led units you can buy are actually lower than 30% efficiency, many lower than 15%..
Even the highest quality (most expensive) companies that use the highest quality leds don't list efficiency. The new area51 panels coming out soon are actually only going to have 40% efficiency. Do you think their ad will say "btw, gavita is 2% better efficiency than our latest and greatest Cob lamp?", because that's basically what's going on.
In order to find efficiency, you have to rip the SPD chart out of the individual cobs datasheets using a pixel reader to essentially count pixels, then do some calculus to find LER. luminous efficacy of source / LER = efficiency.