My wife is an environmental engineer and the incredible size of Amazon boxes for small, nearly worthless items drives her, as they say in German, "Ganz aus dem Häuschen." Fortunately this was from an eBay seller and the packing was minimal. There are even a couple of dents to prove it.
Ricky's explanation for the weight calculation is interesting, and would certainly explain the weight discrepancy between what FedEx showed on their website and what the package actually weighed. Another mystery solved!