The era of "cash in hand" pushing dealers to make deals is over. That may work on a 15 year old car which is nearly unfinanceable anyways, but on cars less than 8 years old with under 100k miles, being willing to finance through the dealer will push them to make deals that they might not otherwise do. It wasn't uncommon for our dealership to agree to a price, contingent upon them financing through one of our preferred lendors. Anymore, dealerships make more money on financed deals than cash deals.
Car buying is slow changing. The fact is that a lot of the negotiating is already done for you- the internet will give you the lowest price in your zip code that can be found and at the push of a button. It was common practice for us to post our new cars at invoice price (we could not go below without being reported by other dealerships- they monitor our pricing and vice versa). You might be able to get a few hundred/thousand more off, but the dealership is eating that loss in hopes to make it up elsewhere (taking a trade in below ACV [actual cash value], a profitable sale of a used car, new car sale incentives from the manufacture, etc). All the old rules may still apply, such as shopping at the end of the month, at the end of the day, shopping previous MY cars, etc, but those strategies aren't as fool-proof as before and there's less money to be saved by doing so.
The best thing you can do is to come into a dealership with a folder of research on a specific car. Find the car you want, in the color you want, print listings of that car in your area at specific prices and E-MAIL other dealers asking if the price listed on the internet is an out-the-door price. Of course they will tell you yes in hopes to get you in, and now you have that in writing. Go to the dealer of your choice and once you find the car you want, use that in your negotiations. Also find listings on the internet of cars similar to your trade-in to help set a value for your trade. They will build up their car and tear down your car to build value into the deal, so you do the same. Finding a few very small hail dents on my new car helped save me nearly $1000. They offered to fix it, but I couldn't care less about the dents so I preferred the savings. Use things like this to your advantage.
Maybe some day, we will see the end of the dealership model. I think we are still very far from that day, however.
