To me, it's not necessarily being the least expensive, but having the best value. When you start to see 360's with Scene It Bundles, or maybe some extra controllers and offerings of free Live Arcade games, things like that, for lower prices, you start to wonder if you'd have more fun for less money, even if it's not the same fun you intended to have originally.
I think Nintendo is afraid of appearing "cheap," really. It's something they've had go against them with the Cube, and so they're trying to avoid that comparison, as well. The truth is, a great bundle can keep the price up, but add a lot more value. You through in another Wii Remote, the motion plus, and Wii Sports Resort, and all of a sudden, the consumer is going to be getting a lot more for $250 than he did before. People would notice, and the average consumer would probably start seeing Nintendo's competition, with the price bottom falling out, as the cheap competition instead, right?