A woman goes into a supermarket to buy some food. The total cost of all of the food she buys is $20.00, but she pays $10.00, with no employees or security stopping her. What is a logical explanation for this?

::: spoiler Answer The woman was 75 years old. In most states, there is a Senior Discount, which cuts prices in half for senior citizens, who have to be at least 60 to apply. :::