Rare and Valuable don't always go hand in hand.
Samba De Amigo had a very limited PAL run (I've heard it's as low as a couple of thousand units) and that doesn't command a particularly high price even with Maracas. I figure this is due to much wider availability (and ease of use) of the US/Japanese versions and the later Wii version.
There are much more common games which go for far more money. Particularly a lot of the better PAL SNES games seem to command good prices, especially in decent condition.