They constitute their own department on a film set and are directed by a key grip. Grips have two main functions. The first is to work closely with the camera department to provide camera support, especially if the camera is mounted to a dolly, crane, or in an unusual position, such as the top of a ladder.
While you might think that paying $2000 for an oil change on a Lamborghini Gallardo is expensive, that is a drop in the bucket when it comes to servicing a Bugatti. A routine service on a Veyron runs about $21,000 which means that for the cost of an oil change you could buy a brand new very non-exotic car.