4 or 5-hrs.
I work with roughly 20 students on their personal statements every year and I've found that it takes about 1hr per draft, with a total of 4 or 5 drafts. So, 4-5hrs total for an essay. That means, in a week, you can have your Ivy League essay or a couple of your UC system essays ready to go!
That being said, I have a very straightforward approach -- some other counselors might prefer that you discover what you want to say through several rough drafts and then patch it up later... It just depends on which process you like.