Amazon offers the Irwin 4-Piece Long Adjustable Wrench Tray Set, model no. 2078706, for $45.67. The price drops at checkout to $36.54. Plus, Prime members qualify for free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $8.14.) That's the lowest total price we could find by $10. It includes 6", 8", 10", and 12" wrenches. Deal ends October 31.
Note that this set is listed as shipping in three to five weeks.