Don't budget, B@M, just go and enjoy.
If it were to be €100 a day, would not be able to afford to go.
Last time when riding in France (2007), was certainly not having to pay more than something like :
Tent place €10.00 a night - cheapest was €4.00/night - and it was good.
Main meal €15 a time - Routier.
On camp site breakfast and evng snack (bread stick, cheese, fruit, etc) from Supermarché, say €10.00 a day.
Coffees, beers, etc €10.00 a day.
Fuel about €25 a day when riding.
Averaged over a complete trip, it would probably work out less. OK, one needs to have cards and an emergency pocket of cash, but if all goes well, don't think the above figures will be too far off the mark - unless prices in F have gone hay wire in the meantime.