Four for $22.49 so $5.69 each.
But seriously, also pick up like one Casio fx260 Solar for $8.49 and a fx-300ESPLUS2 for $12.99 off the shelf at WalMart and try them out. Maybe your students would like some options.
Or look here, the fx-300ESPLS2 is $9.97 in PINK at amazon: https://www.amazon.com/Casio-fx-300ESPLS2-Pink-Scientific-Calculator/dp/B091MJ2GS3/
These ones that show natural math notation on the screen a lot of students have an easier time with.