If you've ever heard of Zappos, you know they're one of the larger online stores, and all they sell is shoes. All kinds of shoes. But the reason they became so successful isn't because of their wide selection, or fast shipping. Though those things were necessary to build their business, what it really comes down to is the way they treat their customers. They focus on the customers before the product, and it shows, and they build loyalty.
Business wouldn't exist without the customers, and all it takes to win them over is thoughtfulness. Get that through your head and your customers will be your best advocates. They'll tell everyone about their good experience, and your business will grow. Here's a story about a woman who's now a Zappo's customer for life because they put customer satisfaction before policy. Give it a read, and think about the last time you were touched by a good buying experience.