Your average peasant is going to make 1sp/day, so 2gp/pound of molasses is a huge investment. And they won't need anti-smoking activists either!

For commodities, as opposed to luxuries, consider using cwt, (hundredweight, or 100 pounds: about the weight of the contents of a full shipping barrel,) as your base unit of measure. Shipping smaller lots isn't worth the effort.

To price, consider what a peasant could pay for a month supply. Mollasses, for example. The peasant pays half his wages for rent, leaving about 12sp to spend. Then he tithes 3sp to his temple leaving 9sp. A pound, (about one pint,) of mollasses would have to last 4-5 months to be worth 1gp! So say a pound sells for 1sp. Average Peasant has limited access to sugar so molasses is necessary, and he may need more than a pint each month!

That makes a cwt of molasses worth 10gp. But wait! The merchant wants 10% profit, as does the vendor, and the transportation costs must be factored in too. So now that cwt of molasses is worth 7gp.

And if the guy buying the molasses knows it is stolen, he might not even offer 10% of the dockside price. That cwt of molasses just dropped to 70sp.

And that's why piracy always fails in the long run. Sure, when nations are shipping vast amounts of gold and silver, pirates can flourish, for a time, but the economics of international trade require many ships operating profitably to build fortunes.

There is a commodity which takes up cargo volume, is expensive to buy, rarely resellable, and absolutely necessary to have on hand at all times: food. More ships have lost their crew or have been taken over by their crew over food than for all other reasons combined.