This is the advice I gave my own children. About sixty percent of people would lie to get something for a lower price. People tend to see money, and many other things, as games. The relative value of an item is somewhere between the person's real need and the sellers ability to emphasize needs to the point of getting a higher price. After all, the seller could always offer a discount or decide to waive an age qualification.
People lie about just about anything from avoiding punishment to making someone feel good.
Yet most people feel like they can trust others most of the time. Experts say many people often resort to a very simple way of thinking about lying. You want something. If you want it, you believe you need it. You will do anything to get it.