• The top 5 cutting and polishing companies are Kristall Production Corporation , KGK Group , Moshe Namdar Diamonds LTD , Blue Star Diamonds , and Bonas Group.

Kristall Production

• Kristall is a Russian corporation that specializes in polished diamonds manufacturing. They also have a 53-store retail chain in Russia.
• The company also produces equipment and rigging for the diamond manufacturing industry.
• Revenue: RUB 12.8 billion (roughly $200 million)
• Its prices of polished diamonds vary significantly based on size, color, and clarity. For instance, the prices for a polished VS1 diamond varies between $10,849 and $33,580 per carat.

KGK Group

• KGK is an Indian-based company that specializes in mining, polishing and selling diamonds. They have also branched out into real estate.
• The company works with DeBeers, Alrosa Alliance, and Rio Tinto. 
• Revenue: $1.5 billion IRP (roughly $21 million).
• Unfortunately, KGK Group did not publish any prices for its polished diamonds.

Insights on Manufacturing Cost

• While recent prices for the manufacturing of diamonds was not readily available, we were able to find a few older sources that talked about the cost to cut and polish a diamond.
• According to a report by IDMA, the cost of manufacturing depends mostly on clarity and color.
• For a Fine 2.5 to 4 carat unpolished diamond, manufacturers spend between $110 and $167 while the commercial 2.5 to 4 carat diamond costs about $89 to be cut and polished.
• The yield varies as well but it is usually in the range of 42 to 48%. This usually translates into a profit margin of 1% to 3% for manufacturers.
• As India is the primary market for cutting and polishing, most of the labor and work is done there. According to an independent research analysis from 2013, "India spends $10 per carat on the polishing and cutting of diamonds, against China's $17 and South Africa's $40 to $60."