In season (December-April and July-August) there are buses that serve the entire resort.  These are completely free of charge. They are very frequent in the winter and much less so in the summer.  It is not necessary to have a car in Verbier, and parking is a real headache in the centre of town.  Furthermore unless your hotel or rented flat has its own parking space(s) you can't park on the street.  You will be ticketed.  So don't come by car!