The primary reason for round being the most expensive diamond shape is that a large amount of the rough stone is lost during the cutting and polishing process. To achieve the fire and brilliance characteristic of the round shape, more of the original is lost than when cutting a fancy shape.

On average, the retail price for one carat diamonds can be anywhere between $2,000 to $16,000, and between $8,000 to $72,000 for two carat diamonds . And of course, the retail price and the resale value of a diamond are very different things.

The most expensive diamond shape is by far, the round brilliant cut diamond. This cut has 58 facets to reflect the maximum amount of light, making it the most sparkly and brilliant of all the diamond cuts. The round cut diamond requires a lot of skill and precision to cut correctly, which adds to its high cost.

A good quality 1 carat diamond ring costs between $6,500 to $7,500 in retail stores, while the same diamond will cost about $3,000 - $4,000 online! On the other hand, the highest quality 1-carat diamond (D color and Flawless) will set you back $10,000 or more (add 40-70% when purchased at a jewelry store).