...how much those cars cost have nothing to do with this conversation.
actually, it does - for two reasons.
First, technology costs money so more expensive cars have better technology in them, like more valves, more cams, variable valve timing, exhaust manifolds that are more header-like, larger catalytic converters, etc. the Ute motor I posted had variable valve timing and was DOHC instead of sohc and a straight six instead of a vee (more torque, but requires a longer front end). So with better stuff under the hood you get more power and efficiency - the price makes a difference.
The 2nd reason price makes a difference is that price has a strong impact on how many of a particular model are built and driven. Monster trucks and top fuel dragsters are legal only because so few can afford them. If everybody started getting them many people would be bothered by the noise and fumes (i love the smell of nitro in the morning!), mad moms would organize, and there would be new laws.
If car pricing is the factor that influences sales so that they have only a small percentage of vehicles being standard size while the majority are compact and sub-compact, then the price is relevant to the discussion - you get a lot less emissions when the bigger vehicles are less common. If everybody in Europe could afford an American-sized car, the laws might be different. So that's the 2nd reason price DOES make a difference - fewer big cars.
Australia is different - way less people so way less cars means way less emissions.
I keep hearing that US regulations are this big problem. If that's true, then can someone provide an example of a country where they are still making muscle cars with 4v carburetors, no egr, open crankcase vents, open fuel tank vents, no seatbelts, no airbags...
If the USA is so horribly restrictive, cars in other countries should be much different, right? If vast hoardes of American lawyers are bullying our poor car companies into making safer cars that nobody really wants, then why do the European cars have seatbelts & airbags like ours. With all the additional freedom they supposedly have, what have they done differently?