some of it is about perception. Pricing a game at $40 is like saying, "yeah, it's not all that great and doesn't have the scope and scale of a Real $60 game. Go ahead and pre-order, or not, whatever." When so much of the industry is about convincing people to buy a product before they can evaluate it's quality you don't want to give any hint up front that it's not a top tier product.
Things are starting to change though so who knows. Torchlight II seems like it is doing alright with pre-orders at $20. But a "full" console game, on a disk? No way.