According to Daily Mail (of all sources) Rockstar's Red Dead Redemption development cost over $100 million. A staggering amount of money, and reports that the game would need to sell 5 million copies to earn back that investment seem truthful.
In speaking with Rockstar representatives Gamereactor learned that Red Dead Redemption was indeed their most expensive project ever, eclipsing the previous record set by Grand Theft Auto IV.
Regardless of how much money was spent on developing the game, the outcome was everything we had hoped for and more as you can see from its perfect score.