Deals like that really don't jump out at me as being so unheard of. Case in point, of the last 3 new cars we've bought, the last being our Av, those were the kind of deals we got on the dealer's "first offer". We've never haggled, and if we have, we left in a matter of seconds and gone on to buy a car at the next dealer. It seems really easy down here in Delaware too, with the exception of I.G. Burton. Imagine this, go to buy a "leftover" '00 300M in October '00, got nice price on the car, but nothing on trade. Left, with the salesman running after us, called another dealer the next day, and got not only a more expensive car at a similar price, and a much better trade figure, on the first offer.
Now with the Av, I used GMBuypower, one of the greatest websites around. Searched all the local dealers with a basic idea in mind (black or pewter, 2wd, preferably Z66). Of the five closest dealers, only one had any 2wds, all four of which were Z66's. Our black 2wd with Z66, bucket seats, convenience pack, and OWL tires, had a sticker of $33,413. Emailed the sales guy, and within hours got a price of $26,411. Breaking that down, it was a $4,000 dealer discount from MSRP, $2,002 rebate, and a $1,000 "old-stock" rebate. Very simple, painless, and easy. All we had to do was get them to value our 300M, and it was done.
That $23k figure isn't far fetched, just take off the rebates, discounts, and figure from invoice. That should be the typical price expected.