Is unobtanium on Pandora worth mining?

(From Avatar where the material is said to be worth $20 million per kilogram)

The answer: it's impossible to know. An article here on space.com goes over whether it would be worth mining at this price assuming a 2% rate of inflation for 144 years, but there is a big problem with this: with only a single reference to money throughout the whole movie, how is anyone to know the worth of a dollar in 2154? Take Turkey for example. Here's a bill from 2004.

 

Yep, it's a 20 million lira bill, because at the time 1.35 million lira was worth a single U.S. dollar. In 2005 the new Turkish lira (Yeni Türk Lirası) appeared and thus a single one of these was worth around a dollar (current value is about $0.67). In the early 2000s then a Turkish movie about the future with a guy holding up a piece of metal and saying "a single kilo of this is worth 20 billion lira!" would look ridiculous (20 billion lira would be about $20,000, certainly not enough to make a profit if it can only be mined in space) but a few years later it looks like a pretty realistic number...and still using the word lira.

Questions about physics and the rest are fair game for a movie, but without any background on what happened to the dollar in the future it's impossible to judge. Actually, the only calculation we can make is one that works backwards - take the $20 million per kilo and compare this with the amount of energy it takes to get to Alpha Centauri, mine it and come back, and then from this we can roughly ascertain the value of a dollar in this hypothetical future. Ignoring inflation, the cost of shipping a kilo of unobtanium would cost $3 billion, and to make a profit we should assume that the value from this kilo is about $10 billion or so...meaning that the $20 million mentioned in the movie is equivalent to about $10 billion today, and thus a single dollar in 2153 would be worth 500 times a dollar today. Your average person then would make about $65 a year working full time.