The Wii console has been in short supply since it came out so some people make money by buying and reselling them at a higher price.
In our area (near Chicago), supply seems to have caught up with demand and you can now find them easily in stores, so you will probably see less of that.
As far as the Wii being special - it just depends what you want. All three consoles have their advantages and disadvantages so you will have check them out along with the games and accessories available to see what's best for you. At the moment the Wii remains the top seller, probably because of the low initial cost, popularity of the Wiimote control and the wide variety of games available.