Every lease, sale or contract for the furnishing of services or for the sale of commodities, or for the fixing of prices charged therefor, or for the giving or selling of a discount or rebate therefrom, on the condition or understanding that the lessee or purchaser shall not deal in the services or the commodities of a competitor or competitors of the lessor or seller, shall be unlawful where the effect of such lease or sale or contract for sale or such condition or understanding may be to substantially lessen competition or tend to create a monopoly in any part of trade or commerce and where such goods or services are for the use, consumption or resale in this state.