I don’t know whether there’s 1000 times as much coal available as rare-earth ores, but it might skew the argument a little compared to 100x.
The real limiting factors are throughput and cost of ore processing. If the process can be done economically at the rate of production, it will be implemented. Even if it barely brakes even in terms of finances, it also helps with A) stopping rare earth metals from going airborne (which is a health hazard sometimes) and B) Creating a strategic backup source of rare earth metals and C) Preventing further environmental damage from additional mining for rare earth metals elsewhere.
https://www.tecoenergy.com/news/article/index.cfm?article=20...
So if you process it all and get high extraction, a couple million Kg of rare earths a year.
(I edited the last paragraph after spotting that I missed a factor in my initial math)
This Appalachian coal is said to have over 300ppm of rare earth oxides in it.
That means for every ton of coal, we're talking about 300g of material. Compare conventional rare earth ores, where for every ton, we're talking about 90kg (Mountain Pass).
It's nice and all that these things are in coal, but thermal coal's already on its way out, Appalachian thermal coal especially due to its high cost and high sulfur content, and a couple pennies of rare earths per ton is a worse use of resources than Powder River coal + actual rare earth mining.