No person engaged in commerce or food commerce, or both, in the course of such commerce, shall pay or contract for the payment of anything of value to or for the benefit of a customer of such person in the course of such commerce as compensation or in consideration for any services or facilities furnished by or through such customer in connection with the processing, handling, sale or offering for sale of any products or commodities manufactured, service or output of a service trade, sold or offered for sale by such person, unless such payment or consideration is available on proportionally equal terms to all other customers competing in the distribution of such products or commodities, or service, or output of service trades.