As of April 2015, a 2-carat diamond ring can cost anywhere from around $11,000 to as much as $97,000 or more, according to The Diamond Registry. A ring that has a 2-carat diamond is more expensive than a ring with a 1-carat diamond because the diamond is not only bigger, but also significantly rarer.
The value of a diamond, and the ring that holds the diamond, is determined by a number of different variables such as clarity, color, cut and the number of carats. Carats are a measurement of the weight of a diamond, but are also often used to determine the approximate size of a diamond. The average price of a 2-carat diamond that is bought wholesale, which is slightly cheaper than buying a single diamond ring, is between $12,000 and $78,000 (approximately), depending on condition, according to The Diamond Registry. Setting that diamond on a ring will cost an additional fee per gram, but will vary greatly between jewelers.
The reason that 2-carat diamonds are so much more expensive than 1-carat diamonds of equal quality is that 2 carat diamonds are as rare as 1 in 15 million stones while 1-carat diamonds are around 1 in 1 million stones. The increase in weight and rarity of 2-carat stones makes 2-carat stones more than twice as expensive as 1-carat stones that have a similar color, cut and overall quality.