Walmart offers the K'Nex 70 Model 705-Piece Building Set, model no. 13419, for $17.88. (Amazon charges the same, with free shipping for Prime members.) Opt for in-store pickup to dodge the $5.97 shipping charge. That's the lowest price we could find by a buck, although we saw it for a buck less two weeks ago. It includes 705 K'Nex pieces and a treasure-chest storage case.