Furthermore, relatively few consultants have an endless stream of work that allows them to just work as much or as little as they want to each week. And, even if they do, some non-trivial percentage of even their working time is going to be non-billable hours related to administration, education, running errands, etc.
That is, don't take your billable rate * 2080 hours/year and compare that as apples-to-apples.