Walmart offers the LEGO Creator Twin Spin Helicopter Building Set, 31049 for $19.57. (Amazon charges the same with free shipping for Prime members.) Choose in-store pickup to dodge the $5.99 shipping fee. That's the lowest price we could find by $6. This 326-piece set can be rebuilt into a snowmobile or single-engine plane.

Update: The price has increased at Walmart; however, Amazon still offers it for $19.57 with free shipping for Prime members.