Walmart offers the the K'Nex 70 Model 705-Piece Building Set for $19.98. (Toys"R"US charges the same.) Opt for in-store pickup to dodge the $5.99 shipping charge. That's the lowest price we could find by $7, although we saw it for $8 less in November. It includes 705 K'Nex pieces and a treasure-chest storage case.