That' true, this kind of ultrasonic edge-sealed earpads must be produced in Dongguan. They can be bought on 1688.com for about 100 Chinese yuan, customized earpads are also cheap, but I don’t like these industrially produced earpads, they all don’t sound good.
This is indeed the role of kennerton pads, making OG 007 sound less dark and sharpening sound a bit, the Asia region does prefer brighter and sharper sounds, like hifiman and some audio-technica are of this type. But I usually don't change OG 007 pads when listening, cause OG earpads from manufacturers like Stax and Sennheiser are usually designed for specific tuning purposes, I regard them as various brand house styles.
The residual value in the second-hand market can show some clues. The transaction price of 007A/mk2 in the second-hand market in China is usually around $1,000 or even lower, which is much cheaper than the price in Europe and US on head-fi. The price of 009 in China is generally $1,600-1,800, which is similar to Europe and US.