Very Rare
Along with the fact that ambergris productivity takes a very long time, another thing that made ambergris a scarce substance is the fact that only 1% of the whole sperm whale population could produce such a substance – most of that 1 % could be found living under the Atlantic Ocean. Well, Steven and Viola must have been very fortunate to find ambergris because the substance is scarce and special.
Contraband
It seemed like Steven and Viola were a fortunate couple. Because they were living in the boundaries of the United Kingdom, what they found was looked upon as merely a particular waste product. If they were in the United States or other countries who banned the act of whaling, they could be arrested or questioned as to how they got the ambergris. In their situation, the ambergris might be seized by authorities and pay the couple a very reasonable price in return.