When it was still expected to be released in 2007, I thought Killzone 2 had a (rumored) budget of $45 Million; and recently Metal Gear Solid 4 had a (rumored) budget of $70 Million. Depending on how delays impacted their budgets either game could be more expensive ...
Regardless of which game is more expensive to develop, Metal Gear Solid is the game which seems like a sound investment from a business perspective.