Overpriced? Yes. But I don't think we should push for high school students to use devices with the power and modifiability of netbooks to replace what they're currently using graphing calculators to accomplish. When I was in high school, students spent enough time in class playing the handful of games that shipped with their TI-83/4's (or obtained them from a friend) that adding more opportunities for distraction isn't ultimately desirable for keeping attention in class and preventing cheating on exams. Sure, some people will always be looking for a means to distract themselves, but that's not an excuse to encourage it.
I also found that most students (in general secondary school math/ science classes) had enough trouble learning anything beyond the basic functionalities of the devices that throwing many times more options on them wouldn't really add too much to their learning experience. A root issue was, of course, that the teachers often didn't know too much about the calculators' functionality themselves, and as such didn't effectively teach much beyond the basics. In many (if not most) of the type of classes that are required to use these calculators, the teaching emphasis is more on learning the mathematical concepts, not learning to use a device that will do it for you with greater efficiency.
For the self-motivated students who are going to take advantage of what capabilities their devices have, a simpler device offers an easier learning curve and quicker route to mastery. One who is interested enough to learn most of a standard graphing calculator's functionality will most likely move on to expand that knowledge with full-fledged devices and software. An example, I had no exposure to programming as a child (as well as fairly limited internet exposure) and the BASIC language on my TI calculator was the first language I learned. It's simplicity left me wanting to do much more, and I went from there to assembly for the z80 architecture of my calc, and from there on to Java/ C++ and beyond.
tl;dr - Calculators should be reduced (substantially) in price, but are primarily used by the average student, not a future mathematician/ scientist. Those who need more functionality will move on to it and won't be overwhelmed by an exhaustive feature/ functionality list at a younger age.