The cost of installation would never include tear out of old flooring. This would be the base cost of new installation and most likely would not cover any costs related to potential issues such as substrate failure etc. If you want to just cover up the old floor with a new floor you will need to consider what you are installing over and what the new floor installation is. Such as is it tile, carpet new wood floor etc. A lot of issues are involved in installing a new floor. It is not just slapping a new covering over the old.