GAP medical cover leaves a GAP in your pocket

Please tell me... how can medical aids possibly keep their fees low when private doctors and hospitals charge 300 - 500% above scale of benefits. So you pay medical aid fees to cover in hospital and doctor charges, then you pay gap cover for out of scale hospital and doctor charges and then you pay whatever is not covered by medical aid or gap cover. Maybe its the coffee in these hotel hospitals that get you through your condition because it seems without extra cash the medical service alone won't.