Quite the interesting questions. Can't wait to plant my first plants. Still getting my FC together.
So I do not think that one food computer comes even close to break even point in a short term (might be also long term) In my mind it is going to supplement our food with healthy additions all year around.
Hope someone with experience can answer your question with actual facts.
I sold it to my girlfriend in a form of a new kitchen top that the FC fits in She is happy to get an additional kitchen top to use.
Nerd farming is fun. Get to play with all sorts of gadgets. To be honest this is my first project with Arduino and Raspberry pie. Its great to have a purpose to use one in a cool project. This project has sprouted lots of new ideas in my head. Like I want to create a tower similar to what the people at http://www.towergarden.com/ have created. I want to have Strawberries and Blueberries all year round Also for some reason my herbs keep dyeing on me. I want to create a system that waters them for me with the right amount. This thing is proven to be the greatest DIY project ever for me