David, actually they will grow large productive plants. I've seen Earthboxes that have full-size plants that are very productive. The amount of soil is less important than the availability of nutrients and consistent source of moisture. Conventional pots may not provide enough of either. They are useful way beyond balconies or other small areas. Our new member TPlant may have pictures of some of the great things he's grown in Earthboxes, Gymgirl is another member that I know that has grown lots of things in self-watering containers. Maybe either one can post pictures.
