Are these not the calculators in question?
https://www.amazon.com/Casio-Scientific-Calculations-Calculator-Functions/dp/B00L3LH3O6
https://www.amazon.com/Casio-FX-991EX-Engineering-Scientific-Calculator/dp/B00ZZ93346
They're showing up as essentially the same price, about $20, to me. Regardless, even the recommended one was $100 more than the other, I'd pay the money. It's stupid to give yourself more headaches than necessary over a paltry amount.
Are you outside the US?