Last night J and I took 15 minutes to pick blackberries. We picked 1 pound 6 ounces. We could have picked plenty more but I just wanted enough for several days lunches. J is now dying to know what the blackberries sell for in store. :) So far we've picked 3 pounds, 11 ounces of free berries. J used to have large gardens as a kid. He says blackberries are the easiest harvest he's done. I might look into a little freezer jam. I use a decent amount of preserves during the year as cake filling.
Edit: Walmart sells 6 ounces of blackberries for $2.99. We picked a total of 48 ounces of blackberries. Our 48 ounces of blackberries would have cost $23.92. Ours were completely free, we did not tend them, water them, or plant them. They are not even on our property!