On my NT I took 55 days and spent around $3k from Anacortes to Boston. So that's ~ $50 a day. I stayed in motels a third of the time, warmshowers another third and camping for the final third. I think $50 a day is sensible as it allows for the odd motel and a good food budget. One thing you must do is eat well and regularly. Do not be tempted to skimp on calories as most of us have normal physiology and need to eat well to avoid bonking.

My daily routine was usually breakfast at a diner if I could find one. Then fruit and energy bars while riding. Lunch might be cheese and salami and flat bread or I'd buy a sandwich....SubWay is a great resource and way to load up on veggies. I'd usually carry two one litre bottles of water in my cages and often Mountain Dew in my jersey back pocket or handlebar bag. Dinner could be chilli, or a can of chunky soup that I'd pick up before camping. One of my best dinners was Chinese in Midland MI....endless rice! I also got into the habit of a Miller High Life after the day was done.