The Wii U isn't so much of a powerhouse that it will cost significantly more than the PS3 and Xbox 360 (or even the current Wii for that matter). But the Wii U's new controller? That'll be very expensive.
How expensive? Nintendo isn't saying. But what they are saying is that they're not even going to bother creating anything more than a one-controller experience for the Wii U, due to "cost issues":
Technically, it is possible for the Wii U to support multiple Wii U Controllers,
We're not planning on asking our customers to buy multiple Wii U Controllers.
The reason being is that a "considerable" price will be involved. Nintendo has also said that the new controller will be the most expensive controller ever.
The Wii U's controller is its main selling point, otherwise it's merely a Wii HD. Consumers have had to purchase an additional controller with nearly every console ever released. Only allowing for one controller per Wii U is going to cause some confusion, and seems like Nintendo is holding back the system's potential.
But seriously. How much is this controller going to cost?