Grey Goose is made from the same water source
as Costco's Kirkland Signature Vodka from the Gensac Springs in
France's Cognac region.
Grey Goose has received lower ratings than the Costco house brand
on many blind taste tests. Competitions where spirits are graded
by blind taste testing, Kirkland scores an 88 and Grey Goose
scores 82.
Incidentally, Grey Goose costs more than twice as much.