I got 2,000 off MSRP, plus free carpet, colored crests, Bose sound system, and heated seats - so it works out to just over 4K off (MSRP). I created a proposal or my dealer - showed him the widely available dealer's invoice, added my options at MSRP, and then tacked on another 5% and labeled it on the proposal as "dealer's profit".

I know it's a Porsche dealer but you can always try...