Target stores currently have a buy one get one free offer for Harry Potter, Pirates of the Caribbean, and Ninjago sets. People over in the forums are reporting that this promotion varies by store, so you may end up with a buy two get one free or a BOGO 30% off in your area. The online deal is BOGO 50%.
Online prices for the most part match MSRP, so 30-50% off is a good way to snag the new Harry Potter summer sets at a discount. You could even buy two Knight Buses and get a bunch of sweet purple elements.