This is not quite correct on facts.
There is a youtube video of a tesla motor being made.
The motors are actually a japanese motor, and tesla makes some themselves.
Theres a bill-of-lading somewhere from the japanese company making some of the motors.
No idea of mix/reason.
Its a std AC induction motor, ie a 3 phase motor like the spindle motor on most machine tools, with a VFD, that Haas calls vector drives.
Zero percent rare earths.
My very old Bp M head circa 1950 has a similar motor, and runs just fine, with maybe 20.000 - 40.000 hours of use on it, and its near silent.
I use a HItach VFD to drive it.
Most other electric cars do use rare earths in their motors.
Again, rationale for one or the other escapes me.
What is demonstrably true, is that AC induction motors are one of the cheapest, simplest, most rugged and powerful motive solutions made.
The 1940s (?) Bp 3-phase motor illustrates that quite well (new motors are much more efficient).
The tesla 300 kW / 500 Hp has a 28 kg mass, iirc, and thus costs approx 240 $ to make.
Anything like that is made at 8$/kg in qty 50k and up, per year.
Its one of the reasons that electric cars will take over.
Motors - cheap. Big motors - equally cheap.
Transmissions - none. Very Cheap.
Most ICE cars cost about 1/3 engine, tranmission, rest to build.
In a BEV 2/3 of that goes away, and the expensive battery subs for them.
But the battery costs dropped, greatly, 2011-2016.
Now, probably 110-130$ / kWh for Tesla, and maybe 180$ in 2013/2014.
And about 80-100$ for model 3, 2017.
At 100$, a 60 kW battery is 6000$. No big deal.
Biggest contaminant is probably cobalt, in the battery.
AC brushless servos do use rare earths, and are extremely efficient, long lasting, and increasingly, cheap.
My 2.5 kW AC brushless servo on lathe is half the size, and 40% the mass, of the 1/2 Hp Bridgeport motor.
We don’t know at what percentage rare earth magnets are in use with EV
but they are. It’s the sum of many small and big motors, generators,
and spool magnets in the industry that makes tons and tons of samarium,
neodym, and all others.