I typically have three to five 500g fruit shakes a day. As much as possible I try to use fresh fruit but it is ok to use frozen fruit also. Currently I have in my freezer frozen raspberries, frozen blueberries, and now frozen blackberries.
For a 600g bag you typically will pay $5.50 to $6.50 for either raspberries or blueberries. So 600g of frozen blackberries for $3.29 was a great deal. I picked up 3 bags.
They are currently on sale at Price Chopper for $3.29.