The Law of Value is a basic law of economics. It says that the value or worth of something is determined by how much people are willing to pay for it. So if something is really useful or useful to a lot of people, it will be worth more money. For example, if lots of people want a new computer, the price of that computer will go up because people are willing to pay more for it. So the Law of Value is a way to explain why things cost what they do.