Left 4 Dead 2 fourpack for PC $134.99 with bonus = 33.75 per person at Steam

Deal at Steam

Pre-Purchase Left 4 Dead 2 - Four Pack

Includes four copies of Left 4 Dead 2 - Send the extra copies to your friends and you'll all get early access to the demo and exclusive in-game baseball bat.

You can also order one for for 44.99 with the bonus baseball bat, but there are cheaper deals elsewhere - do a search in hot deals. Some retailers do not incldue the bonus baseball bat.

Interested in the Xbox360 version? You can get the baseball bat bonus at GameStop, which is offering the game for preorder for 55.99:

Reserve Left 4 Dead 2 and receive a GameStop exclusive in-game American baseball bat. Simple yet effective, the baseball bat is one of the new melee weapons headlining the game, and can only be found at GameStop. Available online and in-store while supplies last.

Online Customers: A code and instructions to unlock the exclusive in-game baseball bat will be emailed when the game releases.

Store / In-Store Pickup Customers: A pre-order card containing a code and instructions to unlock the exclusive in-game baseball bat will be available at time of game pick-up.

link to xbox360 deal on gamestop