Walmart offers the Iris 6-Quart Modular Storage Box 10-Piece Set, model no. 585010, for $21.49$21.97. Opt for in-store pickup to avoid the $4.97 shipping fee. That's $5 under our May mention and the lowest price we could find by $14, excluding the mention below. These boxes can stack and feature a snapping lid.
A close price: Sears has it for $21.89 with in-store pickup.