Today's (April 14, 2013) NewEgg "Shell Shocker" deal has Starcraft II: Heart of the Swarm at $27.99. They're offering free shipping as well.
Be advised, that Heart of the Swarm is an expansion pack to Wings of Liberty as opposed to a stand-alone title. Therefore, it will require Wings of Liberty to be owned, purchased, and installed for it to run.
Amazon has Wings of Liberty listed for $34.60 (http://www.amazon.com/Starcraft-II-Wings-Liberty-Pc/dp/B000ZKA0J6). If you look around, you may be able to find it for even less.
Good Deal Hunting!