Many years ago, someone hit the back of my father’s '63 Plymouth, and it resulted in some damage to the trunk lid. He got estimates from a few body shops, and in his naivete, my Dad went with the one that was FAR lower than the other 3 estimates.
A couple of years later, when the 3 lbs of Bondo on the trunk lid began to crack, we realized why the drastically lower bid was so low. Unfortunately, nobody in my family was knowledgeable enough in those days to know about the Bondo effect.