Zack and Wiki is listed on Buy.com for $18.99 with free shipping. With the google checkout trick, the price drops to $8.99
The google checkout trick is pretty simple. On buy.com you get $10 off your first order using google checkout. But there is nothing preventing someone from making new google accounts to keep getting the $10 off.
If you've been waiting to get this game. Now's the time. Not going to get much better than this.