I disagree with those saying that this game shouldn't be full price. I mean, why should it not? Heck, look at all the people buying football games for $60 every year!
We bought New Super Mario Bros Wii at full price, and it's not unlike a game right off the SNES. NBA Jam was sold at full price back in the day, and it was one of the best selling titles on the Genesis / MD. They just need to fill this current game with enough content that people will feel it's worth spending $50 on, just as it was so long ago.
I'm sure it's possible they're unable to find improvements worthy enough (like NSMB Wii's added multiplayer as its main draw), but I feel like it'd be a wasted opportunity considering how popular this series once was. Maybe some sort of extra mode that uses motion plus for shots? I don't know, but they should find something that works, something worth $50, instead of being forced to budget price it because it plays like a port.
I think we need to get over the idea in which development costs or the length of the games should correlate with the game's price. As long as the game has great replayability and content, there isn't a problem. I mean, over 3 million people in Japan bought Wii Sports at nearly full price. I feel like this is part of the reason we never get any old school (arcade-like) games nowadays, even if they would do well.
I'm pretty sure the average consumer has a very different opinion regarding pricing compared to (us) enthusiasts, as is evidenced by the Wii itself.