I did most of the trans-am and spent about $25 or $30 dollars a day, but i'll admit that I ate well. I was in a group with two friends and we stopped at restaurants every other day. We would regularly stock up for 2 days at a supermarket when we hit one and would buy snacks like ice cream when we ran into them.

I didn't pay for camping or a hotel the whole ride. Mostly we stealth camped and I found a few warmshower.org hosts who allowed us to sleep in their homes or on their yard.

It wouldn't be a bad idea to budget some extra money in case of equipment failure. I just did the pacific coast tour and had to replace my wheel and a cable unexpectedly. You never know what will happen.