When an all-new or redesigned model is first introduced, there's a limited supply and a much larger demand for the vehicle. A lot of car shoppers don't realize how much that affects the price.
For example, the all-new Toyota Prius C has just started showing up on dealer lots, and although the car should cost around $20,000, some dealers are already marking them up by $7,000!
That's completely absurd, but some people are willing to pay that much extra. Don't get caught up in the excitement, just be patient.
Generally, it's best to wait at least four to six months for supplies to catch up to demand. Some vehicles will remain hard to negotiate even after you wait several months, but at least you won't pay as much as you would in the initial "excitement phase".
A great example of how far prices can fall is with the Chevrolet Volt. When it was first introduced about a year ago, some dealers were charging $10,000 or more above MSRP. Now, a year later, GM had to stop production for 5 weeks due to weak demand.
You can now buy a Chevy Volt for below invoice price. That's the power of timing your purchase.