I think I can spend as little as $10 a day sometimes. I could buy a box of granola bars and eat most of those in the morning. Have a sandwich for lunch and dinner. As long as I have supermarkets handy, I can eat for cheap. I could find hotdog stands and such in other towns and spend a few bucks on that meal. Somedays I might slurge a little. I know somedays I'll probably spend more like $20. But I will try to be a minimalist as much as possible.
A lot of people have been skeptical of my pace. But I'm actually training to do a double and triple century this year, and I think I understand better than anyone that a lot of the "suffering" that takes place on a bike is psychological.