Walmart offers the K'Nex Revvin' Race Car 2-In-1 Building Set for $18.74. (Amazon charges the same with free Prime shipping.) Opt for in-store pickup to dodge the $5.99 shipping charge. That's the lowest total price we could find by $6, although it was $4 less in November. The set includes over 370 pieces to build two cars. It requires two AA batteries (not included).