My guess is that the damage to Apple's brand name that occurs with each replacement is larger than the cost of replacing the product.
I once had an expensive brand of computer mouse. After eight months the mouse failed. Later I bought another mouse from the same brand. The mouse failed after 14 months. I stopped buying from the brand. The same thing can happen to Apple, and they need to be careful about the quality of the products they sale when they charge premium prices.
I once had an expensive brand of computer mouse. After eight months the mouse failed. Later I bought another mouse from the same brand. The mouse failed after 14 months. I stopped buying from the brand. The same thing can happen to Apple, and they need to be careful about the quality of the products they sale when they charge premium prices.