Ah, the Kia Rio deal . . .
I simply negotiated the"ad car" at the "ad" price. Well, not so simply - it took 20 hours (total) of negotiating over a month.
First of all, this dealer had been advertising brand new Kia Rios for $5988 for months. I went in with the idea that I would get another Rio financed for about $7,000. Well, they promised that I could get it "close" to that.
Of course they couldn't but I used the leverage that they promised a better deal. They said $8K was the best they could do. I walked saying that's not "close" to $7K. They called me back the next week and promised a better deal. After waiting another 5 hours (remember they are trying to wear you down), they couldn't drop the price any lower than $8K and I walked again.
I went back again the last day of September and tried again and they still wouldn't budge on the price. So now - for the first time - I asked about the ad car for $5988. They told me "no one get the ad car at that price" that I would need an extended maintanance warranty for and additional $3K.
So I kept going up the sales chain of command until I got to the GM. I told her I was promised a better deal and was even called back into the dealership twice with no "better deal" other than to waste all of our times (NEVER lose your cool - acting "hurt" is much more effective than getting angry).
Finally she said there was going to be another ad car next Thursday, to call her Wednesday night and she would either get me a Rio for $7K financed or else they would let me have the ad car for $5988 cash with no further hassles.
Of course, I also reminded them that when their books were eventually audited they could show that they sold ONE ad car at the ad price in the course of two years (to a complete stranger). And that I would give them good "press" on the Internet.
I learned this strategy from an older guy who used to buy ad cars. However, it is not guaranteed and your mileage may vary.