This must be the most profitable item sold in shops.
I suddenly realized that this is what I was paying when I bought a piece of fish in a local supermarket and a very thin sheet of plastic was put on the scales the fish placed on top of it weighed then priced.
When I pointed this out to the shop assistant he said that "it didn't weigh anything"! I suspect this item that weighs "nothing" is purchased by the ton.
There was a study done on this, a few years ago, I can't remember the figures but it was something along lines that as there were several sheets to the gram. It was unlikely to seriously affect the cost of the product.