I'm hoping costs don't sky rocket next gen at a same or higher pace as we saw between PS2/Xbox and PS3/X360. Otherwise, we'll be calling "1M seller" a failure (ludicrous!).
I know of a PC game that slipped 1/2 a million units in its first month and was considered a failure by the publisher and that was 4 years ago.
I know of a PS2 game with > 1million in sales, that was considered a failure.
It's not really about cost, as much as it is expectation, the majority of large developers are publicly traded companies, they don't randomly spend 15+M and hope to make money. The project what they predict they can sell, budget accordingly.
Falures are games that do not meet expections.
Games cost what they do because a certain quality level is required to sell X units, and they are budgetted based on what they are projected to sell. Indeed this is why there are so few novel titles and why in general they are lower budget titles.
What is true is that over the last 10 years the ROI (return n investment) has dropped dramatically in the games industry, but that has as much to do with increased competition in the industry as it does technology pressures.