Ann: Lynas Presentation to ANU Rare Earths Conference, page-9

Partly agree CJ but a few response points.
First the periodic table of elements; if you want to build ANYTHING these are your building blocks.
Lithium is unique in being the lightest metal in terms of its nuclear weight. Batteries need metals switching ionisation (and energy) states. If you want the lightest possible battery Li has a big starting advantage.
The magnetic and phosphorescent properties of REs are also unique; it's the reason they stick out like a sore thumb at the bottom of the table. Usually as the atomic number increases (more positive protons in the nucleus) electrons are added to the outermost unfilled shell (they all have quotas). That's where the chemistry happens. REs are unique in successively filling an inside 4f shell. That's why their chemistry is similar and their magnetic properties unique.
So these guys all have a big head start over competitor elements.
Doesn't mean they can't be replaced if other factors such as excessive costs or materials shortages are against them. (The current price around $100/kg for NdPr seems pretty much a sweet spot in terms of profit for us and affordability.)
There's also inertia; major change is difficult, slow and costly. That works both ways of course; took years for RE demand to recover after the 2012ish price spike and the phosphor market moved on from Europium.
I don't see Tetrataenite as a serious alternative any time soon (and don't know of any advantages it has over NdFeB apart from being less easily corroded).