This is a very difficult question to answer.
Expenses while on retreat will depend on an individual’s personal spending habits, especially in regards to appetite and how one chooses to get around.
Food probably costs about the same as it does back home, with the exception of French specialty items, which are less expensive because freshly baked breads, pastries, pate, cheese and wines are staples in France.
It’s generally 6 Euro to wash a weeks’ worth of laundry (two loads).
If you plan to call home you can always use skype as an app because we have WiFi, so saving on that charge or use your computer, during non “quiet hours.”
Allow for at least one restaurant outing (about 50 Euro for a four or five course meal with wine.)
So, add up your current food budget, your choice of local transportation, a “fun-budget” to allow for meals out, extra treats from the grocery store, perhaps artisanal regional products etc., and you’ll have an idea.