IIRC there is actually a socialist supermarket... it's called the Co-Op, though the words "market" and "socailist" are by definition mutualy exclusive... But anyway iama's expression is wrong.
To make it correct, one should say: "For every product someone takes from the store*, that person must provide the store with one or more different products. All products must be necessities, not luxuaries. *Addendum; the product removed must be approved for removal, so no one takes more than they need."
Not as much fun as your local capitalist market though... ;-)
