Apple invests heavily in research and development and promotional expenditures to maintain among customers the perception of high quality in terms of reliability of Apple product, the interface between its various products, and the attractiveness of both its products and packaging. This reputation for quality:

differentiates Apple from its competitors and allows them to charge a premium price.

Apple has always sold different products that are basically unique. After Steve Jobs invented the PC, the IT industry's former absolute leader, IBM, started offering their own PCs. They even set a standard and all PCs back then were IBM compatible (even Compaq, HP and Dell used that term) or Apple computers.

Apple generally was able to launch more innovative products like the Mackintosh PC and the first OS that actually worked like windows does. Even Windows OS was an involuntary collaboration between Apple and Microsoft. The court ruled that since they worked in some projects together, the fact that Microsoft copied Apple OS and launched Windows was not a copyright infringement.

The same happened with the iMac, iPod, iPhone, iPad, iTunes and about anything Apple sells. Their customers value the uniqueness of the products sold by Apple and their high quality. There are hundreds of different smartphones from other brands, some blow up and burn down houses, others are actually quite good, but they always run from behind. That is basically why Apple keeps selling their products and their customers are still loyal to them.