If that's the case, I should be a Formula 1 engineer

. Furthermore, friends have as well. Maybe folks are used to just driving iffy cars, or simply buyer cheaper bits "Because they all come out of the same factory?"
Granted, it's a truck so the differences should be less, but if an MGB can improve from damper changes (OK, Lever arms to Telescopics), then maybe there is more to it than meets the eye.
I've tried a few in the past. Excluding fancy ones like KWs and fancy Bilsteins, you get what you pay for. My experience?
Genuine : Close to a new car ride; I was stunned the first time I had genuine dampers fitted onto a car after buying pattern stuff, a Mondeo in this case, where I tried many items on the cars due to the miles I did. OEMs wouldn't change the specs by engine size or tyres, if they thought no one would be able to tell the difference

. I'm talking Fiesta and Mondeos here, not Sports cars.
Sachs ; Pretty good. I've fitted a set onto the 325d, and bar the firmness in some cases, the damping isn't far off what I'd want for a daily.
Bilstein : Similar to Sachs. Some I've seen seize on some cars, but that seems to be down to the application and not the damper (I suspect my factory items had seized)
KYB: With these, I did an A/B comparison on my Merc W108. I got the Gas-A-Justs and removed some Bilstein B4s. The B4s have a wallow, albeit a slow-motion one ; They were barely 2-3 years old and didn't have many miles. The KYBs removed the wallow completely which is why I tried them, but were a little firmer; not enough to make you hate the car, but it was notable. That was noticed by 2 other folks who used to travel with me in the car. It's something another friend has noticed, is that KYBs are a firmer damper.
Monroe : Very so-so. A friend fitted a set to an Alfa 156 2.4 JTD, thinking they'd be fine. After all, they're all the same right?

. With Fresh Eibach Springs for the car (Pro-Kit so not mega low), and Monroe dampers, he hated the car. The front developed a nasty wallow, and sometimes would ground out as it wallowed on some speed bumps. As he had a palava changing the dampers (because Alfa), he got sick of the car, and sold it on, with this being simply another contributing factor amongst others.
On a Mondeo, the front end was as it was with iffy dampers 2 months after I changed them. I.e little damping over the bumps, and a 'chatter' of almost no damping on iffy road surfaces.
This is odd as they are an OEM now, under Tenneco, for some very fancy setups. Maybe they don't care about the cars they're not an OEM for, which I've seen before on other parts?
Meyle on a Mk2 Golf : Not as bad as the Monroes but they were a little underdamped and floaty, with a friend getting Bilsteins for his other Golf (a G60).
TRWs : They are fine ; Not genuine good or controlled, but good enough for a daily. If I was saving cash, I'd get a set of these. I fitted a set of these onto our Saab. They don't look like the factory Sachs items (they are half of the size), but they are OK.
The price difference is down to a few things:
-Imports. Most of the big damper companies are in Europe. Naturally, they're taxed more and our exchange rate is poorer too
-Inflation
-Damper dynos ; this is something the cheaper brands will not do, as it's time and money for the car
-Not matching the damper to the car ; basic R&D, but it costs.
I've noticed most car parts have gone up, as have friends, including a chap I know who is a car trader ; he no longer buys from the motor factors for this very reason.
Even with Chinese bits, there are Chinese and Chinese ; There are some outfits from China the OEMs won't touch due to poor processes, auditing (i.e tracking machinery goodness etc.) and practices.