The basis of the plot was the German policy towards Austria under the Nazis before they annexed it in 1938. To save German money and hurt Austrian tourism, Germans were only allowed to spend 10 Reichsmarks a month in Austria.
10 RM was the amount an average worker in 1936 Germany earned in 13 hours, a junior public servant earned about 700 RM a month, could raise a family and pay a maid. In money of 2020 10 RM are considered to be equivalent to $48.