Obviously, inflation, 3-D prices and IMAX prices factor heavily into this. While I *hate* the "follow the money" logic some people use in the Oscar race, I really do have to consider it this year: why SHOULDN'T they give it to Avatar? A movie that, as an "event" as opposed to any possible artistic merit, became a global phenomenon that people are willingly subjecting themselves to over and over. (maybe the same reason Star Wars didn't win Best Picture? Sometimes it really IS about quality instead of popularity)
Especially if Avatar keeps doing upwards of $20 million week-to-week, it's not hard to see it getting too big to ignore.
(Also interesting how it's the polar opposite of Hurt Locker - made just $12 million in theaters, but has been racking it up on DVD sales and rentals. People are "discovering" it for themselves, which says something in and of itself. That's how Crash beat Brokeback [sort of].)