In establishing the cost of a given product to the distributor and vendor, the invoice cost of the product purchased at a forced, bankrupt, closeout sale, or other sale outside of the ordinary channels of trade may not be used as a basis for justifying a price lower than one based upon the replacement cost as of date of said sale of the product replaced through the ordinary channels of trade, unless the product is kept separate from goods purchased in the ordinary channels of trade and unless the product is advertised and sold as merchandise purchased at a forced, bankrupt, closeout sale, or by means other than through the ordinary channels of trade. The advertising shall state the conditions under which said goods were purchased and the quantity of such merchandise to be sold or offered for sale.