Some items are cheaper to buy in season. Blueberries are cheaper to buy in the summer than the winter. Buying a bathing suit or sunscreen in the winter in a cold weather climate will be more expensive than if you wait to go to your warm weather destination and buy it there.
If you wait for the end of the ski season to buy skis, snowboard or a winter coat, a “seasonal item” it will be cheaper. The same is true for summer sporting goods at the end of the season.