[Fat Charlie]

The dealership system isn't set up to deal with customers who know what they want, they're set up to deal with marks who are impressed with shininess and suckers for glibness. If you understand that and know what you want, you can just tell them "I want X and I'll pay you Y for it" and don't waste everyone's time.

If they have no time invested in you and are simply faced with a choice to move a unit, they don't have to hold out for the huge markup. If they know that you don't need to buy a car today and can take it or leave it, they're also less inclined to hold out for the huge markup: some guy who is willing to take a specific car off their lot and won't take up any of their time is an extra unit shipped for no trouble.

It doesn't work if Y is really not a reasonable price for X. They could just laugh and say "No less than Z. If someone sells it to you for Y, let us know and we'll buy our stock from them." If you can't handle that answer, then you're actually one of those high maintenance customers, just one with delusions.

My last two cars were new because I wanted something very specific with the Subaru and it had only been out a few months, and with the Honda there wasn't enough depreciation on them to make used a smart choice.