This means that the emplyees aren't paid as much as they could be, so they're unhappy. If they strike, the businessman won't make a profit. This is yet another risk inherent in capitalism. If no problems occur in production, the businessman still has yet another task to accomplish. He has to sell his product. If people don't like it, or there's too much supply and not enough demand, or the economy as a whole is having problems, he won't make a profit. If the businessman avoids all the possible problems, he will make a profit and have a new amount of money, $Y. He wants to turn this into a bigger amount of money. So the whole cycle starts again... and again...
In short, capitalism, in Marx's view, is unstable; it is fraught with perils for anyone who tries to make more money. Adam Smith had said the economy would keep growing; Marx said that it would grow, but with lots of problems, until eventually the proletarians got tired of the amount of power the big businesses had and revolted. Is Marx right? Will capitalism bring about its own downfall?
People disagree on this. Marx's critics say that working-class people are happier now than ever, not miserable as Marx suggested. Also, we haven't seen any collapse yet!
Marx's supporters say that the economy cam close to collapsing in the 1930s, with the Great Depression, and that more and more people work for large firms, not for themselves.
Whether Marx was right or wrong, we must note that he perceived things no economist before him saw; still, many of his predictions have turned out to be untrue. What he has left to economists is the idea that capitalism is full of problems. The challenge now is to decide what to do about those problems: should we hope that the invisible hand will smooth things over, or is government intervention the answer to recessions, inflation, and other economic problems? The answer, traditionally was no. Adam Smith believed in a laissez-faire ("hands off") policy. That has largely changed in the twentieth-century, especially in the wake of the Great Depression.