The gardai paid a speed van operator €14.6 million last year - but took in less than €7.2 million in fines as a result.
GoSafe has high-viz vans throughout the country, acting on the gardai's behalf to make roads safer.
They've been employed by the force since 2010 to check drivers' speeds.
"Well, I think certainly it needs to be reviewed. The amount of money it is costing the state at almost €15 million a year, is a very large piece of the budget," says Sinn Fein's justice spokesperson Martin Kenny.
"Most people recognise having the speed vans on the road has had an impact, particularly in the area of accident blackspots.
"But that said, it seems to be a ridiculously large amount of money for this service."