I sleep beside the bike, so for each day I figure $0 for accommodation, $30-50 for food (if I'm out east I want lobster at least once), and whatever for fuel (varies depending on your bike and distance covered each day, I am normally $75-150/day in fuel).
This is a pretty bare bones trip and doesn't account for the maintenance that will be required upon your return (or potentially during the trip) (i.e. oil changes during the trip or after ~1-2 weeks I will need tires). Typically I am doing 1000-2000 km/day. I travel with a spare oil filter so it's easy to do an oil change in a store parking lot.
Based on my numbers, a week is no problem if you are camping (probably longer if your daily distances are lower). Hotels will shorten your trip considerably.
Personally I like going east through the US and spending time in mainland nova scotia. Cabot trail is worth doing, but the elevation changes can give you problems with fog and temperature swings, IMHO the roads on the mainland are just as good (without the spectacular scenery). I would skip PEI (sandy boring roads), NB is ok but I didn't find anything special.
