Manufacturers aren’t always able to charge real market prices in a flexible way. They rely of regular reliable order volumes and can’t charge different prices to different customers, and can’t vary prices easily day to day so can’t take advantage of the fact different customers are willing to pay different prices. They also often don’t have distribution and extensive dispersed inventory, so can’t offer different prices to different geographic markets, or different markets with particular volume requirements, or different order/delivery latency tolerances.