Why shall we bear all those costs and others don’t

That sounds like standard supply demand. If you can bear it, and there is no alternative, you will. But moreover as was mentioned there are reasons that may require a product being different prices in different markets as operating expenses are not the same. The simple cost of launching a product in different markets incurs different costs, and thus different prices. That's a trivial example, and with vehicles it gets really complex at the regulatory level, especially in regulatory-rich countries which are common in the EU.

But with the American version you can have a janky mounted door and someone that forgets to install the brake disks

I think their implication is that whenever they're selling in China is kind of trash, and you wouldn't think it's a good deal if you looked closely.