Well, one thing is that the marginal profit of labour is bound to be diminishing at such scale. However, keep in mind that it's not marginal revenue, but profit

Well, one thing is that the marginal profit of labour is bound to be diminishing at such scale. However, keep in mind that it's not marginal revenue, but profit. This means that it's still a viable strategy to increase the amount of employees for them. That drop is not necessarily an issue in accounting terms.