Nintendo fought long and hard to make the GamePad a reality. During the development process, all signs pointed to it being thrown out due to high cost and lack of scalability. Even up until the last minute, the company had reservations about incorporating such an expensive piece of equipment. That's the story out of a recent interview with Nintendo president Satoru Iwata. He was quoted as literally saying that team "almost gave up."
Here's the full quotation: "Sometime during that final discussion [of the system's design], we almost gave up on the idea of the additional screen. This was due to our concern over the expected high cost; it may not have been feasible to create this and sell it at a reasonable price point for the consumers." Nintendo eventually overcame the price obstacle, by reducing the controller's computing power. Instead of incorporating a full processor, it only receives data from a connected Wii U console, which means the user experience will be admittedly limited.
But there is a problem with the fact that the Wii U device is a controller, and for any game console, you need two controllers if you want the most optimized multiplayer experience. Nintendo has said that it will support games with two touchscreen game pads, but that won't happen until well after the console's launch. The only retailer that has actually pinned a price to the controller is a Swedish site with a massive $200+ price tag.