How do you come to this conclusion?
Well, for one I was playing League of Legends for Free yesterday. A game I considered pretty relevant to me, and it seems to a lot of gamers.
I played NSMB Wii last year and, though it was fun, it got boring fast.
Consumers paid 49.99$ for NSMB Wii, I believe there is enough competition nowadays from digital game distro services as well as from mobile games to make people realize that the value of Nintendo's games is highly marked up. Imho it will be increasingly difficult for Nintendo to sustain that pricing model from here on out.
Again, the reason is that others are offering more interesting games at a much better price. Even if a game lasts less long, if the short time I spent on it was unforgettable, it will be worth much more to me than 20 hours of same-old entertainment.