I'm too tight fisted to buy something when I don't have to.
I don't know that I'd run out and buy bags for this. I already have boxes of them all bought on sale in the cabinet. I use them for bagging up snacks for the kids in smaller portions.
Then I discovered how perfect they were for storing just the right amount of side dish beans and peas that I cook from dried. I can freeze those, chopped onions, bell peppers, parsley and even gravies and sauces flat. This is saving me freezer room so well worth buying the bags for.