Produce in season costs less because there's more of it. It tastes better because it was picked ripe, not shipped green from the other side of the world. And it's more nutritious because it hasn't spent three weeks in cold storage.
Most of us lost this knowledge when supermarkets started stocking everything year round. Tomatoes in winter. Strawberries in July. They technically exist but they taste like nothing and cost twice as much.
This site is a cheat sheet. What's good right now, how to pick it, what to cook with it.
Cheaper. Peak supply = lower prices. Cherries in December: $10/kg. In July (imported): $30+.
Tastier. Fruit picked ripe from 100km away vs picked green and shipped 10,000km. No comparison.
More nutritious. Vitamins degrade during transport. A fresh local apple beats one from 3 months of cold storage.
Better for the planet. Less fuel, less refrigeration, less packaging, shorter supply chains.