Monopolies are known to be a negative addition to the economy as a result of four main factors. To begin with, they can set their own prices (really high too, if they wanted), and no one can say anything because the monopoly owns the product and service and can technically do whatever they want with the price. They can also supply inferior products, resulting in lower product quality (for example, if a grocery store knows that there aren't many alternative stores in the area, quality may not be their greatest concern). Additionally, producers will lose incentive to innovate. People will just copy the product and try to make it better, resulting in a loss of creativity. Lastly, monopolies create inflation as a result of the high price rates that they typically set to achieve to maximize their profit.