The price is quite reasonable. This isn't like other systems where you just need the system, a plug, and a controller. If it was just that, then yes, $250 would be quite a bit out of the price range.

With the Wii, you're getting the system, the plug, 2 parts of a controller (that are sold separately otherwise), the sensor bar, and a compilation of games. It's a good value. The Wiimote is $40, and the Nunchuck is $20, that's $60 right there that could be taken into consideration with the pricing. Who knows how much the sensor bar will be separately, but I'm sure it's not exactly a throwaway. The price is very reasonable when you consider what's in the box (just like the PS3).