While my parents would probably not agree, I could make a pretty good case they would have been personally better off without me. The stress of parenting was a major factor in their divorce, with the result that they each experienced years of deep pain, unhappiness, and loneliness. And they are each much less financially secure as they approach retirement than they would have been otherwise. In addition there is a huge range of experiences that they have missed because they needed to be my parent.

Opportunity cost cuts both ways. Parents would say that nonparents don't know what they are missing, but the opposite is true as well. I know couples who decided against kids, who have had amazing experiences together that they could not have otherwise managed or afforded. You might believe that those experiences can't compare to being a parent, but without experiencing them yourself, how can you really know?