The only reason that I ever would consider buying a calculator that is $100+ would be if I absolutley needed it for school, which I do.  This calculator is very pricy compared to your other $20 scientific calculators.  Although, the TI 84+ is a very highly technological calculator, if you will.  It runs very smoothly, I haven't had any problems with mine, and it comes with a manuel if ever questions arise.  I really haven't noticed a difference between the 83 and 84 calclulators but then I never really need it for other than graphing, so I'm sure there is.