If you can reduce legal risk(accidents) by 50x or 100x and extend the road time by 2x or 3x, then paying a security person seems like a doable call. Especially if you can pass some of that premium risk mitigation on to the customer, if load value dictates.
Raw hourly cost may not even be the primary point under the manpower line of reasoning. It is certainly important, but not necessarily the key issue.
