Most child safety seat manufacturers have elected to meet this new standard by providing top tether straps with new forward-facing seats. Most passenger vehicles manufactured after September 1 have the tether attachment hardware pre-installed. Tethers can limit the distance the top of a child safety seat moves forward in a crash, reducing the chance of head injury to a child riding in the child safety seat.
Tethers also make it easier to securely install child safety seats in many vehicles.
However, it is important to remember that you must continue to install the child safety seat with the vehicle's seat belt system when using the top tether. Prices might increase slightly for some models but certain manufacturers have provided tethers for some time. Prices for those models should not increase. I bought my child safety seat a while ago. Once the tether anchor hardware is installed in the vehicle, tethers are very easy to use.