Anecdotes ahoy
I tend to pick up anything worth 5p or more; not that I often see them.
When I was working in a pub in a seaside resort during the off seaon, an elderly lady left her purse on the bench after she and her son had been in for lunch. It had £300 in it.
They rang to see if we'd got it, and we sent it back, recorded delivery.
I got told to keep £20 for finding it. Which was nice.
I found a £20 note outside the police station at the end of my road as a kid. I would have told them, but said police station was never open, so i took it home
i think my parents spent it on cigarettes