Are they copies or genuine plugs that just happen to be made in China? They are defo getting better at faking though. Look at the DV+ for instance, as another example! Unless you know the product inside out, you'd never know on first glance.
On the other hand, a lot of legitimate companies are, and having been moving production to China for a long time now, because of the speed at which China can take a prototype to production. They are world leaders at it. So long as the factory is instructed to produce parts to a certain quality, there is nothing wrong with 'Made in China' per se. The problem is the shady underworld copying stuff using crap materials and poor tolerances.
That's why I only buy parts from the dealers because they have a far tighter grip on where they source their parts from, and they are guaranteed for 2 years.
Yep, Amazon and Ebay are seemingly disinterested in the provenance of the stuff they sell. Again, I only buy things from Amazon that "Prime" filtered and stocked/sold from Amazon EU. I don't use their 3rd party resellers.