All vegetables, fruits and vegetables have a preferential period of consumption (season). During that period its price will be low but outside of it the cost becomes much more expensive. The best option is to plant according to your preference and dispose of the rest of the elements through the purchase.
Over the centuries, some foods have displaced others, whether for human or animal consumption. Potato consumption is relatively recent (200 years) and it displaced turnips and chestnuts in Galicia. The pumpkin has declined and the tomato and pepper maintain a robustness that is hard to beat. The ten basic ones in Galicia are potato, tomato, pepper, garlic, onion, lettuce, carrot, cabbage, cabbage and turnip. In very specific areas there may be broad beans / beans, corn in substitution of any basic on the list.