Jack
First of all, we found the money. It’s ours. It’s not like we’re stealing $10. We’re so lucky!
Also, we would return it if we knew who lost it. But we don’t know who the money belongs to. How would we find the right person? We can’t just put up signs saying “Found, $10.” Anybody could lie and say it was theirs.
Finally, $10 is a lot to us. But it’s not a lot in the grand scheme of things. If we found $50 or $100, I would say we have to work harder to return it. But keeping $10 isn’t a big deal.
We found the money. It’s ours. It is not stealing.
We could return it. But it would be hard to find the person who lost it. We can’t just put up signs saying “Found, $10.” Anyone could say it was theirs.
Ten dollars is a lot to us. If we found more money, we would have to work hard to return it. But it is OK to keep 10 dollars.