Why is gem so expensive?

I'm curious to understand why gemstones can be so incredibly expensive. Is it solely due to their rarity and beauty, or are there other factors at play? For example, does the gem's origin, history, or cultural significance contribute to its high price tag? Are there specific techniques or processes involved in mining, cutting, and polishing gems that drive up the cost? Additionally, how do market trends and demand for certain types of gems affect their pricing? I'm eager to gain a deeper understanding of the various factors that contribute to the high cost of gemstones.