Based on my engineering background, I can speak to the usefulness (think: necessity) of having a good calculator. All through college and graduate school, and even at my job as an engineer, Texas Instruments is the only brand of calculator that I use. It really is the gold standard of calculators. Okay, I’m starting to sound a bit nerdy here, so I digress.
That said, Amazon is currently selling the Texas Instrument TI-30XIIS Scientific Calculator for just $9.99 (54% off!).