Back in the early 90's, Exeter Area High School had an advanced math course that required a TI-81 calculator. I gladly used the course as an excuse to get my hands on this relatively expensive (near $100 in 1990 dollars) but amazing piece of hardware at the time.
My own TI-85, which I upgraded to
for calculus at UNH. It's a bit dusty today.
It cost about $100 when I
purchased it in the early 90's.
I kept my TI with me to the point that my sister nicknamed it a "porta-geek"... (There was even a girl who stole it from me, thinking to wound me for the fact that I wasn't interested in dating her. It had no effect; I obliviously assumed I'd misplaced it in my own absent-mindedness. The story came out several years later, after I'd purchased a replacement.)
The term "porta-geek" is a term I still whimsically apply on occasion to my current daily driver mobile device, my Lumia 950XL running Windows 10. My sister's jibe didn't phase me, either.
By coincidence, I was also in Target's electronics department today. I was surprised to notice that they still had several 20+ year old TI-80-somethings... but rather than the price being lower, the prices are actually higher.
A selection of same-generation TI calculators at Target today (3/20/2016). Notice the TI-80-somethings still going for about $100+.
That said, they were, and are great devices.
I'd love to see a Windows 10 emulator app made out of them.... maybe some day I'll find enough spare time... :)