hi Sonia,
The ball park figure of the Camino is widely given as 1Euro/km so the 750km walk over a 30 day period averages to 25Euro/day if a total of 750Euros is allocated for the walk, as advised by our regular contributor Javier. A fairly detailed cost of every item, meals, accommodation, drinks, etc on the Camino is on our ever informative Sil's posting.
Overseas pilgrims can take, as mooted by several contributors on this forum, two years of planning. We saved and earned one extra Euro/day over the 2 year planning period and we were able to double our available funds for the Camino from 25Euro/day/person to 100Euro/day for me and my wife. We never got to spend that amount, but it gave us much more options .... never had to sleep on the floor or take a cold shower.
My posting tries to give a holistic view of the impending journey, and to try to put things in perspective. There is the initial cost of the equipment, cost of the travel between the home and starting point, loss of income during the walk, so the saving of staying in the cheapest lodgings and scrounging for food plays only a small part of the overall cost.
Leave the cheap end of the travels to the people who are after a cheap holiday, willingness to spend a few extra Euros can open an avenue to many things. On security take the advise of the other posters and keep minimal cash with you, we were robbed of one set of our ATM and credit card but had a spare. Be flexible and enjoy the experience - obviously the more dinero the more the flexibility.