[verelo]

Not to mention, diamond is only expensive because its rare and expensive to produce (and people tend to prefer to real thing...)

Once there is a lot of it, the price drops. Anyone remember the Futurama episode where they go to the gold planet?

[TeMPOraL]

It's neither rare, nor expensive to produce - and people tend to prefer real thing because DeBeers manufactured this trend through a decades-long marketing campaign. An article from 80's covers it quite well:

http://www.theatlantic.com/magazine/print/1982/02/have-you-e...

[zrail]

Diamond is only rare because DeBeers keeps it that way. Raw diamonds are actually fairly common as far as gemstones go.