Mario Kart Wii Wheel also sold separately

If you need additional Nintendo branded Mario Kart Wii steering wheels you won’t have to buy another copy of Mario Kart Wii. Nintendo plans on selling extra Wii Wheels on April 11, the same day Mario Kart Wii debuts in Japan. Each extra plastic steering wheel runs for 1200 yen ($11). Of course, Nintendo’s Wii Wheel isn’t required to play Mario Kart Wii. Ubisoft’s wheel or any 3rd party peripheral should work fine and so should a standalone controller.

With currency exchange rate, the US should costs approximately $15 for the peripheral once it debuts. But no word on US release.

Source: Siliconera