ARS Technica reports Nintendo President Satoru Iwata revealed that the Wii U's second screen was almost axed during the design phase due to their concern over the expected high cost.
The Telegraph interview goes on to suggest that Nintendo eventually figured the cost situation out, suggesting that it will be able to offer the controller for that "reasonable price point" at launch (for Nintendo's definition of reasonable, at least). That price could be more important than ever, as Nintendo announced at E3 that the Wii U would be able to support games that use two GamePads at once, though no such games will be available at launch.
Cost concerns may have ended up limiting the capabilities of the final tablet controller, though. In an interview with Kotaku, Nintendo of America President Reggie Fils-Aime responded to a question about the GamePad's lack of multitouch support by admitting that "certainly there's a cost to [adding multitouch]." But Fils-Aime also insisted that it would have been inconvenient to put the controller down in your lap to support multiple touch points from two hands (though he didn't address the possibility of touching the screen with multiple fingers on a single hand).