Amazon offers offers Prime members the Starcraft II: Heart of the Swarm Expansion Pack for Windows and Mac for $19.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $4.98.) That's tied with our mention from four weeks ago and the lowest total price we could find by $19.

Also available for Prime members (and required to play Heart of the Swarm) is Starcraft II: Wings of Liberty Expansion Pack for Windows and Mac for $19.99 with free shipping. (Non-members can spend $35 or more for free shipping; otherwise, it adds $4.98.) That's tied with our mention from three weeks ago and the lowest total price we could find by $15.