According to the FIA (Futures Industry Association), gold future contracts have grown the most in China in the past 5 years. The amount of increase of demand for gold contract was 416% in 2013, of that compared to 2008. "Overnight trading" is said to be of the reasons for this immense growth.

This is a great example of both scarcity and opportunity cost, since the decision Russia is going to have to make is depending on the scarcity of money that is going to increase if they use natural gas as a threatening weapon towards the countries in Europe. The opportunity cost of Russia choosing to keep trading natural gas for money, is not being able to threat European countries using natural gas.