Medical aids or service providers, who is to blame for excessive charges?

Here is something I have had before on different medical aids that I wish someone would explain to me. Historical when utilizing medical services, one would notice that you pay more than you would than if you where a cash client. The story was always sold with the statement that it is to “subsidize the poor” which was of course hogwash. Over the last decade I have noticed something else. Now recently I did some tests. After the tests I enquired what the cost was and I was told just over R 2000. On the medical aid the claim was submitted for over R 3000. Now lately when you enquire about this the practice or pharmacy will tell you that “This is the rate the medical aid pays”. Here is my question, if a service costs R 100, who gives the medical aid the authority decides to pay R 200 for a service that costs R 100? It is not the medical aids money, it is the clients money. This opens up the door for medical aids to collude with medical service providers to effectively “legally” de***** clients. How can this be? Can someone maybe explain this to me?