Economics calculated in Coffee Pounds. 

Because everyone needs a fixed international currency to compare the market.

Why are cups of coffee a good international currency for comparison?

Direct currency conversions do not show the genuine value of money.  Differences in costs.

A good economic comparator world wide however is the Coffee£, due to the fact that the genuine cost of the commodities (water and coffee) are a relatively small proportion of the overall cost of a cup of coffee.

The majority of the costs are service, rentals, ip, taxed and electrical.