These were ceded to France in return for 4,100,000 francs. The transfer and Monaco's sovereignty were recognised by the Franco-Monégasque Treaty of 1861. In 1869, the principality stopped collecting income tax from its residents—an indulgence the Grimaldi family could afford to entertain thanks solely to the extraordinary success of the casino. This made Monaco not only a playground for the rich, but a favoured place for them to live.