Seems reasonable.
Some items may be overestimated, but that's good as it will be a happy surprise if you spend less.
You will spend roughly $10-15 per day on little things along the way, like snacks, bottled water, Gatorade, etc. Not worrying about spending on these little things will help you get them, you will stay more alert, better hydrated, and enjoy the trip more.
Depending on where you are going, you may want to get a toll road transponder. Getting money/change in bad enough on a car, but on a bike... get a transponder. We did for a couple of long trips going into New England area, and were VERY glad we did.
Then.. ENJOY!!!
So... where is the trip?