In the same interview, Benzies stated, ”it (now) takes 1,000 people to make a game, that’s a requirement… It’s probably more, much more (in the case of GTA5.”
He went on to say that this was ”the way we work now” - the entire company ”works on GTA, or Red Dead, and so on, then we move on to the next thing. And that’s because of the size of the thing, we are modelling at such a minute detail. Once upon a time the car models have four moving parts. Now there are 15 alone in a car’s retractable roof. The detail is ten, twenty times greater than GTA IV, so it takes ten, twenty times more people.”
Of course, apparently 1000 people weren’t enough to make sure the game was stable enough for an online mode.