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It's hard to get hard numbers for development costs, but it can be very, very expensive. I do know that Bungie has up to a $140 million budget for Destiny. A good estimate for a "typical" AAA title like COD or Gran Turismo would probably be $40-60 million dollars.
Kotaku has a list of some estimated game costs, some for development, some for marketing. According to that list, Watch Dogs cost about $68 million to develop, but I've seen other sources give figures closer to $150 million.