I was once a temp worker hired to transfer a bunch of records from an old, terminal-based mainframe into a newer Windows-based app for an insurance company. I spent about an hour doing so and then went and asked the supervisor if their IT department had an old copy of Windows 3.11 lying around (this was Win 98). 3.x had the "macro recorder" that would capture everything - including mouse movement. They did.

I practiced highlighting all the fields, switching apps, and pasting the data. You could only play back at maybe 3x original speed. Then I started my macro running. I had estimated that I could have done it manually in about three days; the macro would do it in about 30 hours and not screw up any of the data along the way. Told the supervisor what I'd done and asked to be paid for two. She said yes and offered me a job on the spot; too bad I was starting med school in a month.

Ditto. During my college internship (1999), I worked the night shift for a certain very large OG domain name registrar. We had a nightly quota of about 200 domain names to take from being registered to the vanilla configuration. Since this was a Unix environment and I was actually learning shell scripting in college at the time, this was the perfect opportunity to script. I received permission from the greybeard running the servers to proceed with the caveat he vetted the code before making it executable. I went from taking almost 5-6 hours to doing my quota in mere minutes. My boss learned of this and told me to keep it a secret from the other techs. He then put me to work writing code to paginate reports and other things. On my last day at the job, I shared the code with everyone.

The second part of that sentence, probably omitted by your boss “… play with computers. The same way we are charging our client for a highly unoptimised process where we charge by person/hour, don’t make it look like it can be done more efficiently or I’ll fire you”

you're lucky he/she didn't kick you out; go and justify "I need 12 people to do something that one person can do in 1 day, alone"