S.D. Codified Laws § 37-10-23
Evidence of advertisement, offering to sell or sale of cigarettes by any retailer or wholesaler at less than cost to him or evidence of any offer of a rebate in price or the giving of a rebate in price or an offer of a concession or the giving of a concession of any kind or nature whatsoever in connection with the sale of cigarettes, if such rebate or concession offered or given in connection with the sale of cigarettes is not offered or given by the wholesaler or retailer in the same ratio with respect to all other merchandise as to which such rebate or concession may lawfully be given which is sold by such wholesaler or retailer in the ordinary course of his trade or business, or the inducing or attempt to induce or the procuring or the attempt to procure the purchase of cigarettes at a price less than cost to the wholesaler or the retailer shall be prima facie evidence of intent to injure competition and to destroy or substantially lessen competition.
SDCL 37-10-23