If you have any do-it-yourself skills you can replace your bathtub drain. You can buy a kit at your local hardware, with all the pipes, connections and other parts you will need. You will also need a pair of needle nose pliers. The only issue you may have is access to pipe that leads from the drain hole, It may be under your tub, in which case you might be able to reach it from the basement or crawl space. Sometimes it will be in the wall and gaining access may be a bit more troublesome. If you can get to the pipe, you can easily do this job and save money from calling a plumber.