Products and services you are offering really needs to be great otherwise sustainability of your business will have issues. Well, you might be able to sell bad products with a good marketing and advertising campaign once or twice, but you cannot repeatedly sell bad product, even when you spend a lot of money on ads. Marketing is important but marketing solely does not determine sales. Therefore, to build a profitable business and retain customers, you need to develop good products that people will want to buy again and again. Sales will flow only when you are selling good products and your customers really like them