It really depends on where you are. In my area a gallon of 5.25% is $1.49 (best price I have seen) and 3 quarts of 6% is about $2.29. 2.5 gallon carboys of 10.5% by weight (the 12.5% stuff by volume of chlorine) goes for about $4 on a refill. There is a one time fee for the carboy at most places that ranges from $4 to $6. It's a no brainer!