It shall be unlawful for chain operators of cotton gins, operating gins in two or more places within the State of Mississippi, to discriminate in prices paid for cottonseed or in the prices charged for ginning services; the necessary operating expenses, freight rates, and other proper elements affecting prices being considered, and the effect of which would be to destroy or attempt to destroy competition at either or any of said places in which said gins shall be operated. Provided, however, that a reduction in the charge for the service herein mentioned made in any locality for the purpose of meeting legitimate competition, or a higher price paid for seed in any locality, when such higher price paid for seed is paid in meeting legitimate competition, shall not constitute a violation of this chapter. And it shall be sufficient to make out a prima facie case of a violation to show a lower charge for the service herein mentioned in one locality than another, or to show a higher price paid for said seed in one locality than another, differences of freight and other necessary expenses of operating business considered.