Well, sugar was still very expensive in 1750. The next year, it started to decline as production levels increased. But most of the French imports in that year came from what is now Haiti, and many slaves were imported to work on the island. African slaves were imported due to their resistance to certain local diseases, and European indentured servants were used with less and less frequency. If you were a wealthy person who dealt with indentured servants or owned property, you would be aware of the decreasing value of European labor abroad and the increasing use of African imports. It's most likely that a person of average means would know the same, but it's impossible to speculate.

Source: The international sugar trade (Hannah)