I am assuming that T&P is tax & plates? If that is the case, there is no margin. All taxes and charges for plates goes directly to the sate. If the dealer has a documentation fee, then that is 100% profit for the dealership, but once in state, the fee cannot be negotiated or waived.
When I was selling at a VW store that also had a Honda franchise, the lower-end Civics only had about a $300-$500 difference between invoice and MSRP, plus about $400 in holdback. So, offering that kind of discount to the dealers is pretty absurd. (I don't know if the invoice-to-MSRP ratio is different there, however.)
Most cars in the US market had a 3-4% margin, plus holdback, if offered by the manufacturer. I remember that Porsche did not have holdback on all of its models, just a select few. With Audi, dealers only got holdback if they met strict criteria, that included CSI scores for bother sales AND service, plus a minimum objective of units delivered per month. The dealer I worked at did not meet any of those criteria, so we were not given holdback. Blah.
Volkswagen just reduced holdback from 3% to 2% on all vehicles in the US. I left the business just before that happened.