Pads should last the camper a long time. They are more durable than air mattresses, which puncture easily. In general, pads are the cheapest of the sleeping accessories, but there is a wide range of prices for all three types. If campers want to spend as little money as possible, they can just use a sheet of quilted with thermowadding and foam.
Sleeping pads are just a solution to providing some layer of comfort between you and the hard surface.