CUPERTINO (AP) — Apple’s largest iPhone is selling for $100 more than its other new model, but an outside research firm estimated Tuesday that it costs Apple only $15.50 more to make the more expensive version.Apple said it sold more than 10 million of the new iPhone 6 and iPhone 6 Plus models in their first three days on sale. Both have larger screens than earlier iPhone models, and analysts say consumers like the new, bigger sizes. The Plus has a 5.5-inch screen, as measured diagonally, while the regular iPhone 6 is at 4.7 inches.The new iPhones went on sale Friday and address a key advantage rival Android phones have long had: size.