Wal-Mart is selling the entry model of the iPad Air for $479, a $20 discount of the list price. Since becoming an official Apple product retailer a few years ago, Wal-Mart has regularly sold new iPhones and other Apple gadgets at cheaper prices than other retailers. Wal-Mart has previously said that it charges less hoping that larger sales will make up lost profit. But this time, Wal-Mart's rivals are matching the discounts.