controlling scale of an object via the scale of another obect

hi i am trying to control the scale of a cue with the scale of two other cubes here is what i am trying. at this point i am newbSmacked by its not working. am i not getting the scale values properly? am i not setting the value correctly?

 public Transform  clarity ;
 public Transform capacity ;
 public Transform cost ;
 
 void Update () 
     {
 
         Vector3 clarityScale = clarity.localScale;
         Vector3 capacityScale = capacity.localScale ;
         float newScale = (clarityScale.y + capacityScale.y)/2; 
 
         Vector3 tempScale = cost.localScale ; 
         tempScale.y = newScale; 
         cost.localScale = tempScale ;
 }

thanks for your help.