Should have pointed them to their own webpage... first paragraph:
Online or In Store: Find a Lower Price and We'll Match It.
If you find a lower price on a qualifying product at a local retail competitor?s store or a designated major online retailer, we will match the price.
At the time of purchase, we will match the current pre-tax price for new, identical, immediately available products from a local retail competitor's store and these designated major online retailers: Amazon.com, Apple.com, Bhphotovideo.com, Buy.com, Crutchfield.com, Dell.com, Frys.com, hhgregg.com, HP.com, HomeDepot.com, Lowes.com, Newegg.com, OfficeDepot.com, OfficeMax.com, Sears.com, Staples.com, Target.com, TigerDirect.com and Walmart.com. We will match prices between our stores and BestBuy.com?. We will also match prices post purchase if we lower our price within 15 days of your purchase.
Best Buy Low Price Guarantee - BestBuy