also, every modern car sold today has anti-corrosion measures, as well as corrosion warranties, so i don't see why you would pay extra for rustproofing. this might've been a good idea 20 years ago, but i don't think it's necessary today.
He'd get the "best price" and then tell the buyer to say, "that includes the mats and metallic paint, yes" (or similar). Basically the guy thinks he's secured it, you hit him for that last bit.
He did a general buying show too.
Re the article - not all dealers are equal: You come back at 4pm, the cheapest dealer has had the alloys switched off or put on cheaper tyres (that's £50 at least). You've no time to go back to the others. You buy? If you don't do you think the other dealers will play your game the next day or just see you as a time-waster?
Why are you adding money to the lowest price they can sell at? That is your target price -- the lowest price they can sell will always be the lowest price that includes a profit (or the smallest loss, for brands like Chevy). Besides, most of the profit comes from the optional packages, which are marked up 200-500%.