My version of a commercially available grow box. I have a real one, a gift, the produced a ton of tomatoes over the last two years, but at $50+, I can't buy too many in good conscience (at that price), when I could just go to the farmer's market and buy the tomatoes. So, I tried the less expensive route. Other than the weed barrier, this was $5 for the bin, $5 for the rocks and $2.50 for the dirt. I suppose $.05 for the watering device, too, but your mileage may vary on that (10 cents in Michigan, for instance).
UPDATES, some of which prove those who post comments are pretty darn smart:
I saw 25' of weed barrier for $7 at our local OSH; if you spread this over 7 bins (a good estimate), it's $1/bin, bringing the total to under $15, including the tomato plants.
The clear bins DO promote some algae. The real one I have (green exterior) just got dumped out, checked and cleaned and has no algae in it. My recommendation - go with something other than clear if you can find plastic you trust.
If you drill or cut holes for the top, make them bigger than you think they should be. I had plants rub against the cuts, and, well: cut plants. So, I have put some paper around the surviving plants (the plants are too big to take out to re-cut the lid). I'm trying to reseed in some of the holes, which should be interesting.
Step 1: Box and Water Layer
It strikes me this is the only unique step in my instructable. I took a box (3/$15 at Costco), and put "Lava Rocks for Landscaping" in as the bottom layer. Note the corner where the rocks do not cover the bottom -- this will be for wick. There is another corner in the front for water.
Step 2: Dirt Holding Layer
Mark where you want the drain hole(s) and drill. I use 2 or 3, as I drill them with a small bit, around 3/8".