This is the reason we assumed a large number of buyers and sellers so that no one buyer or seller can influence price and quantity. Also competition requires that firms are able to enter and exit an industry freely. There are no artificial barriers such as government monopolies or regulations. Freedom of entry and exit does not mean it is cheap to enter an industry it just means that it is not prohibitively expensive to do so. Capitalism relies on the market system to allocate scarce resources among competing wants.
Capitalism believes the least amount of government interference in the market place the better.
But it does recognize the importance of the government in many aspects of the economy. Capitalism also relies on specialization to produce goods and services. When workers specialize it is called the division of labor. Capitalism as well as all economic systems use money. Money can be anything, we usually use paper.