I worked as a contractor for a decade before, I didn't find it demeaning when employees didn't invite me to team lunches or special meetings. Just charge more for your services. Do you care when you get paid $200 per hr, if you are not invited to employee only meetings/lunches? Definitely not. The issue is about the right pay, not so much about demeaning/or that 'caste system' everyone invokes whenever someone sees unfairness.