Often companies will advertise an item at a very low costs to attract customers. However, when the customers go to buy they product they find out the product is not in stock or is different then they expected. Then the company tries to sell the customer a more expensive item.
I went to the car dealership to see the car that was in the advertisement but when I got there I realized that it was just a bait and switch. The advertised car was not there and they tried to sell me a more expensive vehicle.