I haven't read the thread all the way.
But I don't think one can really put a "number" on what is and what isn't productive. There are way too many factors involved. Such as soil structure and fertility, type of plant (beefsteak, plum, cherry etc) variety, how it is taken care of, any amendments added during the life-cycle, and most importantly weather and lets not forget any pest problems or disease.
I can tell you one thing though this year was a bust for me.
I have had a ton of tomatoes but a lot of them were destined for the compost. But yeilds all around are way down from previous years. Last year I probably doubled my harvest at this point with good fruit.