Ultimately Nintendo will be doing constant market research on people's buying intentions and desires. If their research indicated a significant increase in sales if they dropped the price by, say, $50, then they would do.
Nintendo are concerned solely with profitability, as they don't have Gold or PS+ which effectively doubles down on the cost of the console. If they drop the price by a sixth, they would then need to sell over a sixth more consoles to make up the lost revenue. And that's assuming that the Wii U could be profitably sold at $250, if not then they would just be increasing their losses. At the end of the day, Sony and Microsoft are using a subscription based business model, which relies on having subscribers, Nintendo is using a hardware based model, where each unit sold has to produce its own profit.