I just looked these up, and for sub-$5 you get two earphones containing a driver, wireless IC, battery, and a charging case with its own circuitry and battery. And presumably they're still making a profit on that. I don't expect they'll be tuned to sound better than the wired equivalents which are closer to $1, but the fact that they can even make a working product of that complexity at that price point is mind-boggling indeed.
Indeed - there's of course still plenty of exploitation in the world market that puts a damper on the awe for me, but it's starting to feel like science fiction such as Star Trek is becoming reality ahead of schedule. At this moment, I have around fifty distinct objects near me, each with at least one pin-prick-sized computer inside them, and I could probably purchase all of them again with no more than a days wage.
As for audio quality, should anyone be interested: I had also bought a pair of those wired, ~$1 ones, and I'd say that the Xioami J18 have slightly better audio quality, but that's cancelled out by the occasional bluetooth glitches, and the deafening "CONNECTED" message when you turn them on. They also have better audio quality than the ~$25 Sony on-ear headphones by a considerable margin, but that completely pales in comparison with my Audio-Technica ATH-M40x over-ear headphones, which are like having a hi-fi strapped to your head!
