Doubtless the accommodations for the man in the iron mask on the Île Sainte Marguerite were not in the style of the Hôtel du Cap so near and yet so far just a few kilometres across the azure water to Cap Ferrat.
However his dungeon was free of charge.
Eleven years in just a standard room at the Hôtel du Cap would have set him back €3,412,750 (A$5,808,748, US$4,567,965), not including food, beverages, laundry or tips.
And believe me, food, beverages, laundry and tips can well bring that close to double.
If he had chosen a suite or villa his bill would have cleared the national debt of many former French colonies.
It is worth noting that only fairly recently did this and many other luxury hotels in Cannes accept credit cards, previously requiring cash in settlement. They also imposed minimum stays (ten days during the film festival), charged a full booking for early departure, and demanded 50% of the reservation in advance — non-refundable. Naturellement!
Sound and Fury 
Maybe next year?
A delightfully whimsical comment. thank you, Gwen
I have had the pleasure of staying at several of the grand hotels on the cote d’azure,. I still have a few ash-trays to prove it. The pleasure greatly enhanced by having my stay paid for on business. I have dined at Hotel du Cap but alas I have not stayed as a guest.