Think about development costs for both the Xbox 360 and PS3. Imagine if this game was being developed on either of those systems, we could easily see that doubled (maybe even tripled in the case of the PS3), due to excessive costs associated with creating those photo-realistic HD graphics. Also, this game has been in development for under a year and will launch with the console during the fourth quarter of this year, which again would make costs rise significantly would it be made for the other two systems, as even more man power would have to be dedicated to pushing the game out on time.
Now, if the development cycle were a little longer, say 2-3 years, we'd see a significant drop in the development cost, but as it stands now, should this figure be correct, $12.65 million US is not that much money to produce a AAA title.
[Via Zogdog Forums; Thanks Danger-P!]