Marshall developed this concept into 'diminishing marginal utility' - which suggested that as consumers entered a marketplace the more products they can afford to purchase the more comfort they receive. In other words they could only sell goods at the price the market demanded. However, manufacturers focused on reducing costs to maximise profits. Marshall's looked at how manufacturers reacted to changes in market conditions. Introduced the concept of consumer demand and reward.
All labour is productive.
Different skill levels require differing wage rates. Market changes needs to be observed in terms of short, medium and long run time frames. Nature prevented businesses from becoming too powerful.