Since Apple has already established a $10 price point for its productivity iPad apps, such as Pages, Numbers, and Keynote, The Daily is speculating that Microsoft will release around the same $10 mark in order to be competitive.
Microsoft is also working on the next edition of Office that will be fully compatible with OS X Lion as well as the latest release of Windows for PC. Both of these pieces of software are expected to hit shelves sometime in mid to late 2012. An Office for iPad release could occur ahead of those releases, but until there is an official announcement, it is probably safest to look toward the second half of 2012 for this release.
source: The Daily via Neowin