I also think that to some extent car manufactures factor in the tax advantage of a hybrid when they price the vehicle. I really don't think that in our free(ish) market that the government can give a tax advantage (or rebate, cash back, lower interest rate, etc. ) for a product without it being compensated by an increase in the price of that product.
For example the price of HDTV converters seems to have risen now that the government is offering the rebate coupons for them.
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Would I like the government to give me money? Sure. But if say they gave a tax advantage worth $100 towards the purchase of a bicycle, I would expect the price of bicycles to go up $100 (or more). So sure, someone will be making more money, but I'll eat my bicycle if it ends up being me.