The term rare earth is a bit misleading. It's not rare as in uncommon, it's rare as in dilute. Rare earths are elements that don't form concentrated ores, and

The term rare earth is a bit misleading. It's not rare as in uncommon, it's rare as in dilute. Rare earths are elements that don't form concentrated ores, and instead are spread diffusely in common rocks. Most soils contain between 0.4 and 0.8 ppm Thulium. Luckily Earth has a lot of rock, so in absolute terms there are still lots of rare earth material. The problem is that rare earths are mined by processing prodigious amounts of earth, typically the waste from some other mining activity. Like most large scale mining operations, it is labor intensive and environmentally destructive. Naturally this leads to such operations being located where labor is cheap and environmental regulations are lax. When people express concern about access to Rare Earths, they really mean access to materials from countries (often one specific country) with cheap labor and poor regulation. Thulium's expense is due to limited production, as there are few industrial uses for it and those applications that do utilize it tend to need only microscopic amounts, but with high purity.