Not just making the plates but refining the rare earths...
WSJ:How China Beat Out the U.S. to Become the Top Player in Rare-Earths Refining
In truth, the U.S. already has abundant supplies of rare earths, but it relies on China to refine them. That is because the U.S. has lost much of its capacity to process minerals, while China has become the world’s dominant refiner of rare earths, cobalt, copper and many other metals.
...
In the case of rare earths, the U.S. mines around 12% of the world’s supply, putting it only behind China, according to the United States Geological Survey. Most of the bounty comes from a massive deposit in the Mountain Pass mine in California.
But the U.S. exports about two-thirds of its rare earths to China. It has little choice: China is responsible for around 85% of the world’s rare earth refining. Chinese companies then turn the ore into the final product—rare-earth magnets—and export the magnets back to the U.S.
Similarly, the U.S. sends a chunk of its substantial supplies of copper to China for processing. Even America’s lone nickel mine sends its nickel concentrate abroad to Canada for smelting.
Until the 1990s, the U.S. was a major refiner of minerals and metals. But then China emerged as the dominant player, powered by its cheap labor force and looser environmental regulations of a sector that can be highly polluting. The voracious need of Chinese manufacturers for raw materials during the country’s years of explosive growth was also a boon for Chinese refiners.
Today, the sheer scale of China’s refining industry makes it difficult for others to compete. According to industry estimates, the cost of building a refinery plant in China is a third of the cost in the U.S.