When the estate agent shows the villa to M.Pimm she quotes the monthly rental at 7,500,000 francs. In 1963 at the exchange rate of 4.901 francs to the US dollar that would be the equivalent of 1.53 million US dollars per month. In 1963 that villa may have been valued at 1.53 million but would hardly have rented for that much.
Up to the introduction of the Euro EUR, many French people still counted in and spoke in "anciens francs." So 494 anciens francs were worth 4,94 nouveaux, or the number of anciens francs divided by 100. The "nouveau franc" was introduced on 1 January 1960. In this case 7.5M anciens francs would equal 75,000 nouveaux francs or $15,303, a much more reasonable amount.