The Chinese models are cheap because no one is using them. But they can't actually afford (or have capacity) to serve enough people to kill the giants. This is evidenced by them all recently hiking prices or limiting usage.
It's possible that they build out in China at an unreal pace, China doesn't have concept of "community input" to drag down state projects, but then you are left giving your IP to China. Just ask western hardware businesses how well that goes.