The average cost of a half-carat diamond is between $1,500 and $2,500, as of September 2014. While size is an important factor, cut, color and clarity also play a role when pricing diamonds.
Some diamond experts believe that the cut should be the first thing to consider when purchasing a diamond. If the diamond has flaws concerning color and clarity, the cut can make up for it. A well-cut diamond offers a brilliant sparkle.
Diamonds that weigh a little less than a half-carat do not cost as much as those that are exact. For example, buyers pay less for a 0.48 carat diamond than they do for a 0.50 carat, and there is no visible size difference.