The major costs I do not bother to track are food and entertainment. I figure we will most likely eat whether we are on the coach or not, actually we are less likely to eat out when on the coach than when in our S&B. Entertainment such as park admission fees, concert tickets, gallery admissions etc also are likely about the same whether we are traveling or not.
I track fuel cost closely out of curiosity. I am fortunate in that I don't have to limit my travel distance for budget reasons. It is a significant and controllable variable. Travel greater distances spend more, stay close to home, spend less. We are doing some air travel, much more costly than fuel for the same distances, but then again it is hard to drive over the Atlantic Ocean.