(a) Any retailer may advertise, offer to sell or sell cigarettes at a price made in good faith to meet the price of a competitor who is selling the same article at cost to him as a retailer. Any wholesaler may advertise, offer to sell or sell cigarettes at a price made in good faith to meet the price of a competitor if the competitor is rendering the same type of service, has been approved by the department to sell cigarettes at a price different from the presumptive minimum and is not selling the same article below cost to him as a wholesaler. The price of cigarettes advertised, offered for sale or sold under the exceptions specified in this article shall not be considered the price of a competitor and shall not be used as a basis for establishing prices below cost nor shall the price established at a bankrupt sale be considered the price of a competitor, within the purview of this section.

(b) In the absence of proof of the cost of a competitor under this section, the lowest cost of the stamping agent or the lowest cost of the wholesaler, as the case may be, determined by any cost survey made in the same trading area pursuant to the provisions of this article, may be deemed the cost of such competitor within the meaning of this section.