There's been a lot of talk about how the TI-89 is "better than" the 86 and lower. I presume that in a broad sence, we (for the most part) agree. However...
The 82 was one of the first "good" calculators to come out. Shortly after the 85 came out, outshining it's competitor with it's more advanced functions. But the 82 was still more widely used because of the fact it was simpler. Therefore, there were both 82 and 85 users. 82's were the #1 classroom choice.
Meanwhile the TI-92 came out... "with a little keyboard and everything!"
After a few years the TI-82 was improved upon to create the TI-83. This calculator was (and is) an enhanced TI-82, with special financial and statistcal functions. Also, it had a split screen. (Which the 86 does not have.)
A year after the 83 came out, the 86 came out. This was an enhanced 85, and was much more complex than the 83. The 83 is the classroom choice because of it's ease of use.
Afterwards, a TI-89 comes out, creating 3 different levels of calculators, the "best" of which are: the 83, the 86, and the 89. Each of these types of calculators were designed with specific purposes in mind.
Many 83 users still do not buy an 89, because really, why would you buy another? An 83 (or an 85, 82, etc...) is fine for most purposes. If I had $150 that I wanted to spend, believe me, I would not spend it on a calculator.
Some of you need to realize that not everyone is going to run out and buy a new product just because it's "better" than their own, similar one. And do you really think that by saying "the 89 is just so much better" everybodies going to buy one? You better think again.