I just traveled a short distance with a guy from Argentina, we camped in the same place a couple nights. One night was in a city park, the next in a Hostel. He told me that his average was 10 dollars a day. He had about 8,000 miles through north America done, with a couple thousand to go.
Personally I would go nuts eating as simply as he was, rice one night and pasta the next, with bullion and it looked like the occasional hot dog. He had a bag of pretzels.
I spent enough on the three weeks I was out to keep him on the road for months. Not bragging, I usually go cheaper but figured that I was on vacation.

As to my costs on tour, I find it varies a lot from day to day. When I pass a grocery every few days, I stock up on some ramen, those alfredo noodle packet things, bread, pop tarts, some cream cheese or cheddar, crackers, oatmeal bars, possibly some apples. I choose the generic brands if possible. Usually about four days worth of food comes to 25-30 bucks.
Sleeping is anywhere from free to 80 bucks. On my last trip I was in a nice hotel one night, and sleeping in a tent in a patch of woods next to some train tracks the next. One night a campground was ten dollars, another it was 15. The cheaper motels I stayed at were in the forty dollar range. Some nights were wild camping. Over the last few nights there was less of that as hunting season was starting and there was a bit of shootin in the woods all day and night.