Yagoozon via Amazon offers Prime members the Glasslock 18-Piece Glass Storage Set, model no. 11363, for $32.29 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $11.07.) That's the lowest total price we could find by $18. This set includes four rectangular containers, three round containers, two square containers, and corresponding lids.

Update: The price has increased to $33.29.