They aren't that difficult to repair if you have basic carpentry skills. All you have to do is take the sash out and open the side of the frame and you'll have access to the weight and pulley. They're designed to be pretty easy to do. YouTube probably has hundreds of videos on it. You just want to be careful about lead paint if it's an old house and you're producing dust or disturbing old paint.

If your windows are 40+ years old, then sure. But that's not a thing anymore for modern windows.