I think it comes down to replayability, quality of the experience and longevity. In the case of Nintendo platformers, you know that youre generally going to be getting the best there is so you will fork out the full asking price. For other companies be it SEGA, Ubisoft or X there will always be the lingering doubt over if the game will be worth the asking price. Sonic games are hit and miss while Rayman was missing for X Years.
I think if its a new IP, it needs to have something more than just being a platformer behind it to sell. If you look at new IP platformers on Wii, PS3 and 360 there are very few that sold well enough to expand the IP. Outside of movie videogames, there is very little at all. Despite this, we have the low cost platformers selling well as digital downloads - Thomas Was Alone, 'Splosion Man, Braid, Journey, Spelunky to name a few.
With the low development costs that these titles should have, I think a low pricepoint is perfect for them. They dont have the reputation to stand toe to toe with Mario at the $60 pricepoint, so the best thing for them to do is avoid the competition at all costs.
