Actually, supply & demand determine the price, marketcap is just an overall project value based on latest known price.
What is 'Market Capitalization'
Market capitalization refers the total dollar market value of a company's outstanding shares. Commonly referred to as "market cap," it is calculated by multiplying a company's shares outstanding by the current market price of one share. The investment community uses this figure to determine a company's size, as opposed to using sales or total asset figures.
BREAKING DOWN 'Market Capitalization'
Using market capitalization to show the size of a company is important because company size is a basic determinant of various characteristics in which investors are interested, including risk. It is also easy to calculate. A company with 20 million shares selling at $100 a share would have a market cap of $2 billion.