It is a common misconception, that you cannot negociate the price of a car. let alone a Porsche or any other hi profile brand. It all comes down to the market at any given time.
It is also said that you cannot get rebate when you buy a Rolex, IWC or most other hi-profile watches, but nonethelesss, it is pretty easy to get 15-25% discount if you offer to pay cash here-and-now.
I think the same applies when buying a car.
In some countries the dealer's margin on a new car is big and so naturally they can discount if they want to and secure a sale that way.

I think it's total BS that you cannot get a rebate as a virgin Porsche owner.
Of course you can. And why would you get a rebate the second time? Loyalty rebate? And if so..what will you get if you buy a third Porsche?

Congrats on your car!! And a merry Christmas to you, mate!