Its a rigged economy if teachers require a certain type of calculator for class...essentially spending others money.
Much like text books.
TI has pretty much cornered the market in NY. All students are *required* by the state to have a graphing calculator for algebra, geometry, and algebra II. I teach Geometry. The vast majority of my students rarely even needed a scientific calculator - just a few times for trig functions, and for square roots. Other than that, the arithmetic was pretty simple.
However, NY also came out about 5 years ago and said that school districts may NOT require students to purchase graphing calculators. They can't even charge a refundable deposit to borrow one from the school. NY state schools are required to provide the calculators to the students. So, there's even less incentive for TI to lower prices. The only distinction is which districts are still using the 83+/84+, and which are using the N-spire.
It's absolutely amazing how far it's gone toward technology - many students can solve problems ONLY if they have the same calculator that they learned on. Their only explanation of how they solved a problem is "I pushed buttons." Probability problems have been posted here in OT quite a few times. A simple to understand and calculate probability problem might be, if the probability of a player winning at a particular game in a casino is 3/7, what is the probability of that player winning at least 8 out of 10 games? To solve this problem (to meet the NY standards) requires zero understanding - a student just needs to know which buttons to push on the TI-83+ (or beyond) calculator. Well, at least to answer the questions on the state assessment. That wouldn't fly in my classroom... You do it the long way. If you're really nice, I'll show you how to do that, and 50 other questions on the graphing calculator in the two weeks before the state assessment.