However I shared the paper's central question which was the complete lack of existence of a trading class. In other cultures there were always traders and markets and points of exchange. Perhaps as a mono-culture the Incans never had to develop such systems (or the need was small enough, as pointed out in the paper, that they did so on a case by case basis).

Other than the lack of a trading class the economy is very much like the early Egyptian economy, based around the production of food and with taxes extracted in the form of labor and food. My guess for the lack of a trading class is due to too few neighbors to trade with.

And actually one of the fairest. We all are equally rich in time so requiring labor in equal amount makes sense.

Then you can give everyone equal money for their labour and let them trade the surplus goods and services on the free market.