twenty something and annoyed

someone explain to me why an eye exam at one location can cost $75 but the same exam at another location (of the same company) can cost $100 simply because the doctor is not on an insurance coverage plan. BUT i don't have optical insurance so why would it matter if he's on the plan or not? I'm so confused and frustrated. I just want to order contacts. They fit, I can see perfectly and there are no problems. Can't i just order them? UGH