Do I have a right to know how much a consulting firm makes versus what they make by my work?

I work for Manpower Consuting and MANY of us feel we are severly underpaid by them...How can we find out what they make versus what we make? I am personally in the lowest 5% for what I make in my career field, according to Salary.com. Also, can I take my contract to a different firm once my initial 6 month contract is finished? Or does Manpower own the position?