Since there's an approximately logarithmic relationship between headcount and productivity, you can keep 60 devs busy doing the work of 5 devs by virtue of each of them becoming as productive as 1/12th of a developer.
That's definitely true of some teams at Amazon. If you're working as an "away team" as they call it, it can take months to get even a one-line change reviewed. It can take a couple of days or more just to figure out how to submit a review request for the "host team".
