It's not that unlikely. Consider that the offices may have to push significant amounts of code/data back and forth between their offices and their data centers. You probably want to minimize the amount of developer time wasted.
Consider this question: Let us say the cost of an infrastructure at google HQ is X. X is the cost regardless of internet. Now let us say you have Y which is the price of an average inernet connection for google offices. Or you pay 4 * Y to get that connection. Ok lets make it 10 * Y. Whatever. The point is that if it makes your workers a bit more productive (5000 people?) lets say 3%. I think that 3% productivity on developers translates to WAY above the price of that connection.