I wrote a paper on the Communist Manifesto and wrote a section on this supposed problem of the capitalist skimming profits off the top.
"Marx points out something very interesting. He points out that the worker always gets paid less than what he actually produces. If a worker produces 1000 toys in a week, he might only get enough money to buy 400 of them when he receives his paycheck on Friday. Marx argues that this is exploitation; the worker creates the product and the capitalist, who does no work on the product, skims some profit off of the top for himself.
In this analysis, Marx leaves out one incredibly vital component of all voluntary interaction: time. The worker is willing to take the job, because he would rather gain goods now than in the future. Imagine a man is hoping to get a car for his family. He could go out and mine the ore needed, meld it himself, create an engine, and create all the necessary parts for the car. He would gain 100% of what he produced, because he is working for himself alone. This would take him an extraordinary amount of time to do, though. He wants the car sooner rather than later. Because of this he is willing to work a job to earn money with which he can buy a car much sooner than he could ever make one himself. He is willing to allow the capitalist take a portion of his product in return for getting his car sooner.
Let’s look at this same story from the capitalist’s point of view. He has a wealth of resources, both in capital goods (factories and tools) and in cash, which he hopes to increase into more wealth. He is willing to pay the worker $100 now in return for higher profits in the future. If he could not skim some profit off of the top, he would have no incentive to hire the worker and the worker would have to spend much more time and energy to get the car he wants. What’s the point of paying $100 out today in return for $100 in a year? Why not just hold onto it then?
As we can see in this thought experiment, the capitalist and the worker are not at war with each other. They are not hoping to achieve contradictory goals. Their purposes are harmonious and only the free market will allow them to come together to achieve their subjective goals. Dr. Hoppe explains it concisely and precisely:
Without the capitalist’s expectation of an interest return, the laborer would be worse off, having to wait longer than he wishes to wait. And without the laborer’s preference for present goods, the capitalist would be worse off, having to resort to less-roundabout and less-efficient production methods than those which he desires to adopt."
Hope that helps. Those who claim this as a problem of the capitalist economy completely ignore time preference and marginal valuation.