Years ago, when I was naive enough to think I could understand business planning and investments, I read a lot about Return on Investment (ROI).
This morning I picked beans from the potted pole bean plants. This is about the 5th or 6th picking. Not bad for the price of 4 bean seeds. (Of course I've not factored in costs of soil, water, fish emulsion fertilizer or labor.)
To me this is a great ROI - especially since the labor is free..