Apple and Samsung are two great examples of higher end companies whose products aren't appreciably superior or inferior to most of their competitors, but through relentless advertising, they have made themselves seem distinct from their competitors.
A significant function of advertising is to reinforce decisions. Very few people buy a car because they saw an ad for it, or a iPhone, for that matter. But the ad serves to reinforce the decision of those who already bought the product, decreasing buyers remorse. It's the reason most higher end car ads are selling the idea of a car rather than the car itself. Ditto with the older iPhone and iPods ads.
And a similar thing is true for low end, cheap products. People buy Coca Cola over store brand cola because of the brand identity coca cola creates. They may be totally unaware of it, but it's just enough of an impetus to push someone to spend the extra $1.50 on a 12 pack of Coke vs another brand.