A comment from a Peruvian friend of mine, who I passed the article onto:
"This is incredibly misleading. There was no market because that culture was run by theocratic totalitarian blood thirsty central planners. The vast majority of people were a form of slave and trapped in basically a completely rigorous caste system. They were a mix of India and NK, ruled by a Mao "god" Inca who had total control of everything. The article gets right that people had to pay tax as labor but in some cases also as a percentage of the food they gathered, and a non-trivial percentage was stored in "tambos" (http://en.wikipedia.org/wiki/Tambo_(Incan_structure)) to support the military and state-controlled trading routes.
OTOH the Spanish monarchy was totally evil, purposefully wiping out millions of people and creating basically what amounts of royal satraps in the new world from which to extract cheap/free labor and tons of gold and other wealth.
That said, the Incas were also primitive--no real written language and barely a minimum system for tracking amounts and numbers (http://en.wikipedia.org/wiki/Quipu).
I took 12 years of Peruvian history and it wasn't until recently that I realized how utterly terrible the Incas were. They were proto Marxists."