Thanks for the pointer/reminder. It's a great piece on the economics of not-so-rare-earth mining, in fact I'm pretty sure it's where I first learned that rare earths aren't.
But it doesn't touch on the question that I asked. That might be because I phrase it obtusely.
If China either turned off the tap, or hiked the prices (by politically punitive amounts, not economically rational ones) I'm wondering how long the disruption that caused would last? Long enough to be noticed, or not? I'm sure major users of the end products have stock on hand, but would their reserves last until alternative supply chains are fully operational?