Amazon offers the Microsoft Office 2011 University Edition for Mac, model no. W6L-00001, for $89.99 plus free shipping for shipping. (CyberPCs via eBay offers the same.) That's the lowest total price we could find for this version by $2. It features Word 2011, Excel 2011, Outlook 2011, and PowerPoint 2011.
Orders placed by Friday, December 19 are guaranteed to arrive in time for Christmas.