Buying and running a car needs a lot of money, even more for a good quality one that is not too old. There are a lot of things to pay for - the car itself, fuel, parts (for example, tires/tyres), maintenance, repairs, insurance to cover the cost of crashes or theft, parking charges and road tolls and/or any tax or licensing fees charged by government.
If many cars try to travel around an older, or badly built town, that was not designed for cars, this can make these problems worse, and cause danger to other road users, for example people riding bicycles or walking. But, designing a town layout where everything is made for cars as the main transport can cause other problems. These include even more pollution and traffic, as everyone has to drive. Communities are divided up and separated with roads. People walking are in danger by expressways with too few foot bridges, small road bridges or other crossings. Designers now understand these problems and try to build more balanced systems.