I’ll bet I’m not the first videographer who as been asked this question. It’s insulting on a few levels. It conveys the idea that you can’t possibly be making a living doing your job. It also implys that you do something your client sees as play. Yet they have not a clue how to handle even a simple edit job.
This question comes from envy and ignorance. Your client wishes they had a job like yours. Asking this question indicates they have no idea how to reach that goal.