It doesn't have a real effect tho...
If they decide consumers will buy at X price, they'll sell them for X and the people willing to spend X will buy it
If there's a 7k tax credit, they'll sell it for X+7k, and the same amount of consumers will pay X and buy the same amount of cars...
The only difference is everyone is paying their share of those 7k bonuses to manufacturers.
That tax money would be much better spent on infrastructure or public transport.