I just realized that the Changda SFN40 (warm white variant test here) is more or less identical to the LHP531; the LED chip size and footprint as well as the 3x3 arrangement are virtually identical. I thin 4800-5100 lm should be possible with the cool white LHP531.
I need to measure the SFN40 in cool white and an XHP50.3 HI also in cool white, both 70 CRI, as these are the real competitors to the LHP531.
By the way, I know why the LHP531 / LHP73B is probably so cheap. They use the same chip, just in different numbers/arrangements. Due to the extremely high order volume, they can probably push the price per emitter down significantly. I wouldn’t be surprised if LMP and Changda use the same identical LED chips from the same manufacturer.