(1) It is unlawful for any person engaged in commerce or food commerce, or both, in the course of such commerce, either directly or indirectly, to discriminate in price between different purchasers of commodities, or services or output of a service trade, of like grade and quality or to discriminate in price between different sections, communities or cities or portions thereof or between different locations in sections, communities, cities or portions thereof in this state, where the effect of such discrimination may be substantially to lessen competition or tend to create a monopoly in any line of commerce, or to injure, destroy or prevent competition with any person who either grants or knowingly receives the benefit of such discrimination, or with customers of either of them.

(2) Subsection (1) of this section does not prevent:

(a) Differentials which make only due allowance for differences in the cost of manufacture, sale or delivery, resulting from the differing methods or quantities in which the commodities are sold or delivered to purchasers.

(b) Persons engaged in selling goods, wares or merchandise, or service or output of a service trade, in commerce from selecting their own customers in bona fide transactions and not in restraint of trade.

(c) Price changes from time to time where in response to changing conditions affecting the market for or marketability of the goods concerned, such as but not limited to actual or imminent deterioration of perishable goods, obsolescence of seasonal goods, distress sales under court process, or sales in good faith in discontinuance of business in the goods concerned.