The Wealth of Nations by Part 1 Chapter 11 Page 133

every other luxury and curiosity, is likely to increase among them. But as statuaries and painters are not likely to be worse rewarded in times of wealth and prosperity than in times of poverty and depression, so gold and silver are not likely to be worse paid for.

The price of gold and silver, when the accidental discovery of more abundant mines does not keep it down, as it naturally rises with the wealth of every country, so, whatever be the state of the mines, it is at all times naturally higher in a rich than in a poor country. Gold and silver, like all other commodities, naturally seek the market where the best price is given for them, and the best price is commonly given for every thing in the country which can best afford it.

Labour, it must be remembered, is the ultimate price