If they use those planes for other reasons (search and rescue, fire, etc.) then the cost is minimal. If the pilot weren't out there catching speeders he would

If they use those planes for other reasons (search and rescue, fire, etc.) then the cost is minimal. If the pilot weren't out there catching speeders he would be doing touch-n-goes, etc. to maintain currency. Pilots have a minimum number of hours / approaches per time period, and planes have high fixed operating costs (annual service, hanger, etc.), combined the marginal cost of catching speeders is low.