Seems very bizarre, but I can't imagine there was a nefarious intention all over $10. Seems like an agent who was looking for a problem, but also willing with a solution. It's odd, but probably not that big of a deal.

That said, DL doesn't really offer services like this usually, so I'm curious how the transaction actually went through. Did the DL agent actually process the financial transaction? I've never known any DL counters to sell any luggage/packaging at the check-in counter, usually referring to an airport vendor or nothing. And, more importantly, was this "additional collection" for the Amex card?