Monopolies are a very evil kind of market. When there are many companies producing a good they would produce a certain amount of a product and sell it at a competitive price that would not be too cheap but not be too expensive since if it made it too cheap then nobody would earn money, and if they made it too expensive then their rivals would make money.
But monopolies make a small amount of products that are extremely overpriced for what they are. They can do this since there is no other company to oppose them and they can do whatever they want with the price.