I was curious as to trade good such as molasses, chocolate (coco beans), tea, coffee, and spices would be thrown over the side in favor of more useful or easy to trade items such as perfume, silverware, furniture, glassware, etc...
A cargo of indigo dye might not seem of value to a pirate unless he does do a little smuggling on the side. Of course the rope, sails, barrels and other materials on a captured ship would have value.
With the Navigation Acts the English Colonies may have a desire for such luxury items cheap.