This image below succinctly describes the absurdity that is supermarket portioning of vegetables. The packet (out of shot) has a price tag of £3.00, reduced to £1.45, due to its proximity to the sell by date. The pods are apparently 500g of broadbeans. When shelled, the green beads barely covering the bottom of a milk pan, weigh 100g.
There are 62 beans in the pan, making the cost per bean at 5p. Or 3p per gram. These might be tricky to grow, but if you have a bit of garden space, some string and a few bamboo rods and a ton of slug pellets, they might be an economic choice for grow your own.