Hi, Moira,
Welcome to the forum! Your costs will depend on whether you stay in public albergue vs. private albergue (public around 6 €, private around 12, pension or hotel more than that) and whether you eat in a restaurant (average meal price in a basic restaurant with a menú del día will be around 10 €) or buy groceries in a store. Also, how many coffee stops or beer stops will you make, that can have an impact as well. Washing clothes in a machine, usually around 5-6 € vs. washing by hand, free.
I don't know if you are a joiner, or if you know about this group, but Chicago has a pretty active chapter of the American Pilgrims. They have lots of helpful people there and have monthly walks. I'm downstate and have never been able to make it up, though I have good intentions!
@jpflavin1 (another forum member) walks with them regularly but he is currently walking the Via de la Plata.
https://www.americanpilgrims.org/chicago-illinois-chapter
Buen camino, Laurie