That isn't entirely true though. People don't buy things just because of the way they work. Whether they admit to or are aware of it or not, they buy things for many less logical reasons, such as the way the product looks, how it gets them attention from their friends, the brand's social status or image, etc.
Apple could sell poor products and millions would buy them because it says Apple on it. That's what happens when you have a cult following. Eventually, the market would figure it out and Apple would lose their popularity. Perhaps it would happen much sooner if the product was really bad. But still, the fact that people buy things doesn't make them good.
As it stands right now, Apple can easily sell mediocrity, possibly sub-mediocrity. I don't think they can get away with selling total garbage.