Sinenome,
I agree with all the other people above, but I can offer you also my very recent experience.
I just finished my trip in late October.
You have to count on 5 to 8 Euro for the accomodation in the Albergue (in Galicia the Albergue is donativo), 7 to 8 Euro for the pelgrim menu, which has 3 courses and includes wine/water and is quite filling, 3 Euro for breakfast (usually in a bar and consists only of toasted bread, jam and coffee). Then you will have to purchase some fruit and lunch (usually bread and cheese/meat) in a shop for say 3 Euro. Water you fill up when you start, at the bars and at the fountains, so don't buy! This brings you to 22 Euro max. If you enjoy a beer (or two), fruitjuices, more coffee or chocolate (all 4 cost tou about 1 Euro each), then add 4 Euro, bringing the total to 26 Euro.
The exchange rate at present is US$ 1.18 for 1 Euro, so we are talking about 26 US$ /day for the basics and US$31/day for the basics with beer and coffee. Mind you that the exchange rate might fluctuate 5 or 10% up or down, and also you have to take into account full albergues and emergencies. Cheap single rooms (habitaciones) above bars, in 1 star hostals or casas rural, or private will cost you between 10 and 20 Euro ( for doubles between 15 and 25 Euro)
Kees