You're paying $100 for completely antiquated hardware where its core feature is "it doesn't do much".
Pretty much any professional environment that you will need calculations will have access to a computer that can do these calculations significantly faster and better.
I thought my HP was pretty cool in high school, but pretty much the moment I graduated I stopped using it because I figured out how to use Excel and/or a programming language to do number crunchy stuff. Even for CAS stuff, I would just use Wolfram Alpha or SageMath (depending on how ambitious I'm feeling with setting stuff up).
I can't remember the last time I used a calculator outside of showing someone else how to use it.