But the difference is always there, hiring the first guy is more difficult by the same factor as running the first agent. The relevant comparisons are between one agent and a thousand agents (original setting) and between one guys and a thousand guys (analogy). In both cases the costs will be a thousand times higher and you can achieve a thousand times more in the same amount of time, so the correct measure is time times number guys or time times number agents. The difference between adding one guy and adding one agent is irrelevant for my point and that is also pretty obvious as that crosses the boundary between original setting and analogy.
You might want to make a separate point about the cost difference of getting more done by hiring more people or running more agents, but that is a different point.
No, the article is about what can be accomplished now vs what could be accomplished previously. That it is much cheaper to run thousands of agents at once than to have thousands of employees is directly relevant to that question.