I worked for two very rich men, each was a Billionaire many times over. Over many years I noticed each almost always started working before 8AM (which is when I usually arrived) and they were usually working when I left. I know they frequently worked weekends because they called me from time to time from the office to my home.
I'm sure some inherit, I am equally sure many really earned what they have.
Most wealth is created via the difference between what a person's labor actually is worth and what they are actually paid by their employer(s). I have no doubt some wealthy people actually do work hard, but the vast majority of their wealth is still created through other people's labors.
@snytiger6 I view it as the employees helped the wealth creator reach his/her goals and in the process were paid for their efforts. Remember the employees were given direction.