In this old thread I compare the cost of chlorine sources. The prices are old (and Ben, please fix whatever broke with "code" blocks), but basically bleach and Cal-Hypo aren't that different in price, bleach being a little cheaper. In some areas of the country, Cal-Hypo is cheaper than bleach. I think you are getting your factor of 1.7 price ratio because you are using a higher price for Cal-Hypo than one can get if one buys in quantity. Nevertheless, bleach at a good price is usually the least expensive source of chlorine (other than chlorine gas you can't get).