Where your dollar buys more

In Venezuela, Fidel's friends have created opportunities;

Prostitutes more than double their earnings by moonlighting as currency traders in Puerto Cabello. They are the foreign exchange counter for sailors in a country where buying and selling dollars in the streets is a crime -- and prostitution isn’t. Greenbacks in the black market are worth 11 times more than the official rate as dollars become more scarce in an economy that imports 70 percent of the goods it consumes.

It's about survival;

The benefits of the trade are stacked around Elena’s room in the Blue House brothel -- bags of rice, flour, sugar and cooking oil -- products that other Venezuelans have to line up for hours to buy at regulated prices in shops, if they can find them at all. 

On the black market you pay 71 bolivars for a U.S. dollar, rather than the 6 you'd pay on the official forex market regulated by the government. But at least the black market actually has dollars, often brought into the country by foreigners who have to travel there on business. Like sailors.

What's the socialist excuse?

In a country where prostitution is legal, it is the black market in dollars that Maduro has called “perverse,” saying it was designed by the bourgeoisie to destroy his Socialist government. 

Economic rationality has a way of dealing with socialism. True.