I do currently have 2 Chinese guns, A TF89 and and older B-3. Neither one is really a gun you'd even want to run 500 pellets through. Rough firing, lots of kick, cocking cycle sounds like the spring is full of rocks, overall not well made at all. The only reason I have the 89 is someone else didn't want it and offered it free, just pay shipping. I did consider buying a 99 a while back, but every owner I talked to said to forget about it, don't waste your money, so I bought an R-10D instead. I sometimes will shoot my HW50M or HW35L for an entire day on and off if I have nothing else to do, but the behavior of the Chinese guns make you not want to use them for more than a few minutes. So far, the only real redeeming value that some Chinese guns have to offer is a decent barrel. The Chinese do seem to have gotten that part right, at least in some of the higher-end models like the QB-78/79.
Just how much work do think goes into one of those guns for the price you pay? Not long ago the JM spring was an option on the TF guns, about a $20 premium over the normal gun if I remember right. For that price, what you get is a simple spring swap, no more. Theres no "working over" as you say. Giving one of these guns a "real" tune-up using the JM spring would add at least $50-$75 to the cost. It's a bit labor intensive to go through any gun. You need to pay someone to do it, and to sell the guns as you suggest in any volume you'd need a whole factory full of workers to turn them out in the numbers you perceive.
100,000 triggers? I doubt that HW even built that many for their own guns, let alone to sell to Compasseco so they could put them on unliscenced reproductions of HW guns! Also, again, theres that labor thing. Just how many people do you think work at Compasseco? Certainly not enough to install tens of thousands of triggers per year.
You're right about not really liking Chinese guns, but it's not because they don't work well or whatever(some apparently do), but because they (the Chinese makers as well as the importers) are taking advantage of unknowing buyers. They frequently quote power figures well above reality,(even more so than most other makers) and advertising can lead some people to believe that they are just as good as the R-9, HW-97 or whatever they are a clone of for a fraction of the price. A good many Chinese rifles are even dangerous- if you're not careful with a cheap Chinese springer(especially the breech-loader underlevers) you could easily lose a finger or two. That B-3 I have is just such a gun. No safeties or beartrap latches, an accident wating to happen. It's the fact that many unknowing buyers get a Chinese gun and expect it to live up to the claims made. Many end up with a gun thats non-functional in a week with no support from the manufacturer, or with a gun that works but isn't at all any fun to use. The lack of quality control in Chinese airgun factories insures that buying an airgun from them is a crap shoot, maybe you get a good one, maybe you don't. Thats the kind of experience that turns potential future airgunners away from the sport.
I'd rather spend a bit more and get a gun that is built to much higher standards of quality, and one I know will last for many years with out breaking anything major. Heck, I have a couple 30+ year old Diana rifles that still have their original seals and springs intact, they still work like new. I don't think I have ever seen one of those German air rifles come from the factory with steel chips in the compression tube, or a compression chamber full of grease, or a stock finish that looks like it was dipped in mustard.