[sliverstorm]

I've heard the other reason is their math libraries. I don't know a whole lot about the calculator industry, but I've been told the number of companies with good embedded math libraries is very small, and the cost of developing one is prohibitive.

This adds big barriers to entry. You can't write your own libraries, and you can't use more powerful hardware to compensate either- TI's calculators cost them very little (the popular TI-83 uses a CPU designed in 1976), and will shove you right out of the market with their huge profit margin.