On my shorter tours, I usually spend about $15, mainly because I bring a stove and cook all my meals, and camp.
On my upcoming pacific coast ride, im budgeting about $20-25, because I will be bring cold breakfasts/lunches, but eating out for most dinners. I'm planning on eating at the local restraunts mainly, but fast food now and again never hurts. Like the others said, camping in OR and CA is pretty much free, $5 or so, while when I camped in Montana, some of the sites there were close to $15, and WA is about that much too.