In the past, a full expansion had a cost of $30 and it was just the game, no additional "free" months.
If you're waiting for it to be bundled, I'd guess it'll be 12-18 months before we see that considering we do not have a release date for the expansion.
EDIT: Currency is US$
Edited, Aug 5th 2012 11:17pm by xypin
Signature starts here.