The unethical and illegal practice of a business promoting an item at an especially attractive price with the intention of convincing customers to buy something else that offers the business more profit.
The business is likely to begin a bait and switch by telling customers who want to buy the promoted item that it is of inferior quality or is sold out and no longer available.
Another link: http://en.wikipedia.org/wiki/Bait-and-switch
Bait-and-switch is a form of fraud, most commonly used in retail sales but also applicable to other contexts. First, customers are "baited" by advertising for a product or service at a low price; second, the customers discover that the advertised good is not available and are "switched" to a costlier product.
The goal of the bait-and-switch is to persuade buyers to purchase the substitute goods as a means of avoiding disappointment over not getting the bait, or as a way to recover sunk costs expended to try to obtain the bait. It suggests that the seller will not show the original product or service advertised but instead will demonstrate a more expensive product or a similar product with a higher margin.
Non-retail use of bait & switch tactic: