Toys R Us is presently offering discounts on all Transformers DS games. 

Buy one Transformers DS game, and get the second for $10. This makes for a great opportunity to purchase both of the new ROTF DS games that have just been released for $40 total instead of the usual $60 ($30 each).

This promotion applies to Transformers games on the DS, not specifically ROTF, so presumably this could be used to purchase games from the first movie as well as the recently released Animated game.