Amazon offers Prime members Spy Kids 4: All the Time in the World on 3D Blu-ray / Blu-ray / DVD / HD Digital for $4.75 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping adds $4.98.) That's at least $5 less than you'd spend at a local retail store for the non-3D version, outside the offer below.

A close price: Target charges the same for the non-3D Blu-ray edition.