[bumby]

The vast majority of security investigations are done by the govt Office of Personnel Management and paid for by other government agencies with appropriated funds. What contractors may often pay for is hiring someone and then paying their salary while they wait for the clearance to go through (i.e., they pay for them to do something else while they wait for the clearance to do the job they were actually hired for). But that's more about their hiring pipeline than the cost of clearance.