Asimov said:
I want to answer one plot hole that has been brought up- why is unobtanium worth so much? Well, because it's from Pandora. People will pay shitloads of money for anything exotic or rare, to showcase their money. Gold has almost no use to the average person, but people pay tremendous money for it because it's shiny and rare.
At the scale the humans were mining it, I doubt it.
Early settlers mined gold because of its place in human society. Until only the past 100 years has gold wavered as the most common form of currency. Essentially, it WAS money. So to settlers finding gold in land was like finding money that grew on trees. The Gold standard is still used today; all of the paper money we use is backed up by gold that the United States owns. [link url=http://en.wikipedia.org/wiki/United_States_Bullion_Depository]Fort Knox[/link] is infamous for its status as a gold depository, and the Bond film [link url=http://en.wikipedia.org/wiki/Goldfinger_(film)]Goldfinger[/link] focused on a plot to steal the gold from Fort Knox, sparking an economic crash of epic proportions and rendering Goldfinger an economical magnate.
Unobtanium on the other hand, has no such status in human history. I find it the most massive plothole in the entire damn film. Men fight and die for the procurement of this resource, which is so valuable that companies will pour trillions into obtaining it. Cameron seems to have really forgotten the human element of the equation in his little movie and spent all his budget into rendering his lush rainforest that basically looks like a bunch of [link url=http://transformers.wikia.com/wiki/Fuzor]Fuzors[/link] from Beast Wars. He just made the [link url=http://whatisthematrix.warnerbros.com/apu/rv_cmp/article_rv_adam_01.html]APU[/link] mech suits from The Matrix and gave it a windshield.
Cameron's Pandorapedia calls [link url=http://james-camerons-avatar.wikia.com/wiki/Unobtanium]Unobtanium[/link] a "room temperature super-conductor for energy" which somehow makes it worth 20 million for a kilo, about 2 pounds.
From Cameron's little wiki thing
"Without Unobtanium, interstellar commerce not be possible. Unobtanium is not only the key to Earth's energy needs in the 22nd century, but it is the enabler of interstellar travel and the establishment of a truly spacefaring civilization. Making a feed back loop, the more Unobtanium is mined, the more ships can be built, and more mining equipment can be sent to Pandora."
Maybe Cameron should have told the audience the importance of this crap instead of a little one liner telling us about the cost? Maybe he should have underlined that Earth wants it for energy to expand into the stars and to move beyond Earth? I mean this all this fluff was written to underscore just how "bad" and "unsustainable" humans are to the "pure" and "wholesome" natural majesty that Cameron gleefully displays in the film.
All of Cameron's work reflects his view of the struggle between nature and mechanics, and the ultimate triumph of nature over the mechanical. Aliens pits the raw natural predatory instincts of a brooding monster against the cultured, mechanical order that humans use in space. Terminator is a contest between remorseless, unchanging march of the corporate machine against the raging, unpredictable spirit of humans. Even Titanic showcases the sparkling testament to humanity's ingenuity and engineering destroyed in a single blow by nature. Avatar is nothing new; perhaps an update that lets Cameron show off the latest in special effects and give his spin on current themes of the energy crisis and American imperialism.
When it comes down to a contest for exploiting aliens in 2009 films, I found District 9 to be Avatar's superior in every way, its much more intelligent, had bloodier action, and was funnier than Avatar. Its aliens were also much more complex and interesting to watch; every time one was on the screen I found myself examining it closely, an activity I didn't have forced into my face like every one of Avatar's alien wildlife closeups, just begging you to stare and drool at it like a coverpage of Maxim magazine. Great job, you hired a legion of computer animation majors and gave them 10 years. If it had any less quality I could only be disappointed. Back on the point, District 9 was in every way just as poignant a meditation on human nature as Avatar, and wasn't as predictable, except in the good ways when you think to yourself "oh he gon SHOOT HIM" and then delivers that moment with gleeful, impish energy.