What you are not including above in your 100k per year/ 50 per hr metrics is the amount of non billable hours required to land a consulting contract. Depending on the situation, a consultant may only have 1000 billable hours a year. That comes out to $100k per year at $100 per hour. Now throw the need for health care, retire savings, etc and the $100 per hour does not seem that high.
It's true that regular employees don't quite work the same way. There are company outings, seminars, meetings which are included in the salary. Someone online working on just one project and sometimes being monitored (I find that ridiculous) is constantly focused on the end-goal, at least in theory.
I doubt there are any freelancers who always have jobs lined up, so the 100k per year can quickly become 50k a year.