The real cost of a manual process is not the hours
When someone describes a manual process they want automated, they almost always lead with the hours. Six a week on invoices. Two days a month on reporting. It is the easiest number to reach for, and it is usually the least interesting one.
The hours are real, but they are the smallest part of the cost. What actually hurts is the error rate. A person copying figures between two systems will get a small percentage wrong, every week, forever, and those errors surface somewhere expensive and much later. By the time a wrong number reaches a customer invoice or a regulatory filing, the six hours look like a rounding error.
The second hidden cost is latency. A manual step does not just take its own duration, it takes however long until someone gets to it. A task that takes eleven minutes of work can add three days to a process because it waits in someone's queue over a weekend. Customers experience the three days, not the eleven minutes.
The third is concentration of knowledge. Manual processes accrete undocumented judgment. This vendor always sends the total in the wrong column. That client's reference numbers have a prefix nobody else uses. None of it is written down, all of it lives in one person's head, and it leaves when they do.
This is why we start engagements by watching the process rather than reading a description of it. The hours are what you notice. The errors, the waiting, and the single point of human failure are what the automation is actually worth.