You don't pay for just the IC and PCB, you are also paying for the in my opinion, fantastic API and documentation that comes with the teensy. Plus, access to a platform that is fairly popular and its users seem to be more, well, advanced, than most arduino folks. Because of this, the forums tend to skew towards less noise and more technical matters.

They are expensive, yes, but I am comfortable buying a board from them every few years to use as my main chip.