Iirc, theyre the last products still using a z80, which was launched in the seventies. Keeping an entire chip fab open for one thing isnt cheap, even if its for something like a z80
At the same time, there's no reason why they couldn't upgrade to something else. You can do everything a graph calculator does on your cellphone using websites...
Why allow calculators at all then? People who are better at using it have an advantage, everyone should only use pen and paper for the SAT, that's a level playing field.