What combination are you trying? I think lego batman two is just listed because it's the trigger game for the promotion... as far as I can tell there isn't a single combination of lego batman 2 games that come up as B1G1 free
This is true, in store the sales tag actually says (19.99 Value) for the free item of which most if not all the Lego games (aside from Lego Batman 2) and the strategy guide are price.
EDIT: Just saw, even the online add has the 19.99 value graphic on it as well.
By the by, some if not all stores have a Buy 2 for $15 on all clearance games priced $9.98. A lot of junk titles, but if you're into Playstation Move a majority of the launch window titles are all 9.98 now, and I've seen copies of Far Cry 2 (Multi), Glory of Heracles (DS), Dream Trigger (3DS), De Blob 2 (PS3) and a few other decent games that fit the deal at 9.98.