8oz $8 makes 40 gallons = $0.20 gallon
32oz $16 makes 160 gallons = $0.10 gallon
i make 2.5 gallons a brewday ($0.25), thats plenty for the two 15 gallon batches and then i pitch it. i spend another quarter the next brew/transfer day. i'm sure i could get by with half a gallon a brewday...