This might only get at part of your answer, but as a starting point I'd encourage you to check out my previous answer to a question about the value of French currency in the early 19th Century — aka, the time when The Count of Monte Cristo begins. A few key points from that:

• 19th Century French authors like Dumas tended to use "livre" and "franc" interchangeably to refer to the same currency
• The value of major currencies like the pound and franc tended to remain pretty stable throughout most of the 19th Century, outside of crisis periods, though some things did change of time (wages for certain jobs went up or down with economic trends, for example)
• A range of examples for what things cost in early 19th Century francs (an unskilled laborer earned about a franc per day; a typical noble family earned 5,200 francs per year, etc.)

EDIT: Something else that can be helpful to understand with regard to 19th Century French currency is the gold coin alternately referred to colloquially as a "Louis" or "Louis d'or" or a "Napoléon," depending on the politics of the time and the speaker. These coins were typically worth 20 francs.