Along roadsides in most countries in Africa, farmers and traders sell pyramids of tomatoes, string bags of onions or oranges, or bowls of beans or flour. Selecting the best-looking produce at the best price takes time and good bargaining powers. But farmers may be short-changed with this method of pricing, which rather haphazardly puts a price on their produce and their labour. Selling produce by weight may be more likely to give farmers a fairer price, but is a big change for traders and buyers.
You might like to browse our archive of scripts on small-scale enterprise, which include scripts on financial management for farmers, how supply and demand affect prices, and choosing where to sell: http://farmradio.org/english/radio-scripts/enterprise.asp 
Does this story ring true in your broadcast region? How common is it for farmers to sell by the heap, or by the kilo? You could investigate what difference this would make to the prices charged and to farmers’ incomes. If it is common to sell by the heap, ask farmers and consumers if they think it is fairer to sell by the kilo – and why.