Advertising
In the United States, advertising itself is a big business. Millions and millions of dollars are spent on television, radio, and printed messages to prospective consumers. Advertising firms do "market research" for their clients, testing out various "pitches" in the quest for ones that are effective.
From the viewpoint of American consumers, advertising functions to inform them about available products and services, as well as to encourage them to buy. From the viewpoint of visitors from abroad, though, advertising serves an additional function, and it affords countless insights into American values, tastes and standards. From American advertising, foreign visitors can gain some understanding of these and other aspects of American society: American ideas about physical attractiveness in males and females, American ideas concerning personal hygiene, the emphasis Americans place on sex, speed and technical sophistication, the amount of faith Americans have in arguments that include specific numbers, materialism in American society, male-female relationships, both pre-and post-marital, the attention Americans pay to the words of celebrities, the characteristics of people who, in Americans' eyes, are considered "authorities", whose ideas and recommendations are persuasive, and the sorts of things Americans find humorous.
By comparing advertising they see in the States to what they have seen at home, foreign visitors can gain understanding not just of American society, but of their own as well.
Pricing
With few exceptions, Americans are accustomed to fixed prices on merchandise they buy and sell. The usual exceptions are houses, automobiles, and sometimes major appliances such as refrigerators and washing machines. Another exception is a private sales. Americans are not accustomed to bargaining over prices, and in fact usually feel quite uncomfortable with the idea.
Foreign visitors must realize that the price marked on an item does not include the sales tax that is added as part of the payment. (Sales tax rates vary from one jurisdiction to another.)
Americans do not believe, as people from many cultures do, that a commercial transaction includes particular attention to the human relationships involved. They look for the item they want, decide whether they can afford the price marked on it, and, if they want to buy it, find a clerk or salesperson to take the money or do the paperwork for a credit-card purchase.
People who try to bargain for a lower price in a shop or store are likely to be considered either quite odd or startlingly aggressive.