How would you choose the world’s top five diamonds? By cost? Carat? Who owns them?
People occasionally pay insanely high prices for some unique stone, but a diamond’s monetary value depends on social factors that change over time.
That’s why you can’t go by price. Wealthy people certainly pay for excellent quality, but they also buy gems to impress other people or to fulfill some other inner need; or to possess something that was once owned by somebody they admire; or for historic value; or for a multitude of other reasons.
Jewelers, of course, cater to social factors, but at the business level they have to judge a diamond objectively. They go by: