Walmart offers the Melissa & Doug Shape, Model, and Mold Clay Activity Set for $9.97. (Amazon has it for Prime members for the same with free shipping.) Opt for in-store pickup to avoid the $5.99 shipping charge. That's the lowest price we could find by $8. It includes a 9.5" x 9.5" x 1.5" wooden tray, five wooden stamping cubes, three rolling pins, four tubes of modeling dough with molding lids, and one patterned wheel press.
Update: It's now out of stock at Walmart; however, Amazon still offers it for $9.97 with free shipping for Prime members.