It takes about 350 grams of wheat to make one loaf of bread. Offer to sell each item to the highest bidder. Probably, the bread will invoke more interest than the pile of wheat. Determine which items are agriculture related. The concept of value added can be further investigated by tracing a particular product and its cost back to the original product and its cost.
Potato chips are an excellent example.
Estimate the cost of the original product and then trace the processing back to the original potato. There are many facts that you may discover. Special potatoes high in starch and low in sugar are needed to make potato chips. Nutrients are lost because the potato is exposed to light and air during processing. Water jets and caustic soda are used to remove the skins of the potatoes.