This is the most popular diamond shape. A round diamond has more flexibility when it comes to balancing cut, color, and clarity grades yet still maintains its brilliance and fire that is why it is generally preferred over the fancy diamond shapes.
There are two reasons why a round diamond is more expensive than a fancy-shaped diamond on a per carat basis. First of all, as this is the most popular diamond shape, there is a high demand for it. The next reason is because the yield is low which means that more of the rough stone is wasted when cutting a round diamond.