Amazon currently has a pretty good deals for some The LEGO Batman Movie sets that are 25% off the retail price. First is The Batmobile (70905) which is at $44.96. This makes the set a good $0.08/piece ratio and you get four large wheels as well. You can take a look at my review of the set here.
The other set that has good deal is the Batcave Break-In (70909) which is at $74.96. With the sale, the set is at a great $0.07/piece with a lot of exclusive minifigures including three Batsuit variants. You can take a look at my review here.