You're missing the king of them all: De Beers.
A few not-so-well-known facts for you:
* Diamonds are not even close to being the world's most rare jewel. They are not even considered to be in the category of rarity. Emeralds, Rubies, and most other well-known jewels are more rare by several orders of magnitude. However, Diamonds cost more, all because of DeBeers. They hold a global monopoly on the product.
* Unlike Microsoft and other companies cited for being monopolies, this one is not only a Monopoly but uses its status in the way that we fear those other companies would. They control the entire supply and only release a limited amount. If they release enough that the price might drop, they force a buyback so that it raises up to prior prices. All this happens while the price of Diamonds would be far, far less than it actually is if it was controlled by multiple competing companies.
* Strongarm techniques used by DeBeers to gain control of mining sites are well known. Families have been threatened with murder and rape, and on some occasions the threat has been carried out. Either way, DeBeers gains control of the mine one way or another.
* DeBeers was seen as such an unhealthy and immoral organization that they weren't allowed to trade in the United States (!!!). They did business in the U.S. through subsidiaries and trade partners, and did advertising in the U.S. however to keep the demand for diamonds up. They are being let in again however after paying a 10$ million price fixing fine (Only ten million for decades of diamond price fixing??? Jeez...)
For information on the business side of De Beers' evil plans, go here:http://pages.stern.n...ng/debeers3.pdf