This is the Congressional Budget Office Cost Estimate as ordered reported by the Senate Committee on Commerce, Science, and Transportation on July 10, 2019. From the Document: "S. 1601 would require the National Highway Traffic Safety Administration (NHTSA) to issue a new regulation requiring new passenger vehicles to have a system to alert the driver to check the backseat after the engine has been shut off. The bill also would require NHTSA to contract with an independent third party to complete a study on retrofitting passenger vehicles with technology to eliminate the risk of children being forgotten in the backseat. Using information from NHTSA, CBO [Congressional Budget Office] estimates implementing those provisions would require one additional employee, several passenger vehicles for testing purposes, other equipment, and additional funds for the third-party study. In total, implementing the bill would cost $3 million over the 2020-2024 period, CBO estimates. Such spending would be subject to the availability of appropriations."
Congressional Budget Office: http://www.cbo.gov/