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.

Dubai is deemed as one of the cheapest places to buy diamonds and rightly so. There's a reason that it is regarded as one of the world's top three diamond trading centers—the other two being India and Belgium.

In general, diamonds do not increase significantly in value over time. Outside of a small number of rare or colored diamonds, the vast majority of diamonds have decreased slightly in value over the last few years, making them a poor investment from a price appreciation perspective.

The price of diamonds fluctuates in the economy just like any other high-end good. Sometimes diamonds increase in value, while other times they decrease. Regardless, pre-owned diamonds sell for slightly less than their original prices. In most cases, a diamond has a resale value of 20-60% of the original price paid.