Vehicle window excess almost double the cash price

I submitted a standard vehicle window replacement claim for the rear passanger door window with outsurance for my Chevy Optra (standard car all government ppl drive) and the excess given me was R950 which apparently does not include my smash n grab which I didn't stipulate. Outsurance send out National Auto Glass to come and do the fitting and after an hour and a half they are unable to fit the window and they sub-contract the work to someone who can actually fit the window. Upon them completing the job they advised that they charge R500 cash price for such a window fitting and supp****. Now my question is why must I pay near double the cash price just for an excess which is supposed to be a portion of the cost. I will be changing from Outsurance immediately. Thanks for nothing Outsurance