First, you have to go through the process of opening a bank and meeting all of the regulatory requirements. Second, you have to apply for a national charter for your bank from the Office of the Comptroller of the Currency. If your bank is able to get a national charter and becomes a national bank, then your bank IS REQUIRED by law to pay 3% of its paid-in capital in exchange for shares in ONE of the Federal Reserve district banks. Therefore, if your bank has $5 million in paid-in capital, then you are required to send $150,000 to the Federal Reserve District bank that oversees your area. Then, and only then, your bank becomes a member bank of the Federal Reserve System. For a bank that size, your annual dividend would be $9,000.
The amount that a national bank must subscribe to in the Federal Reserve District bank is set by law. A member bank may not hold any more or any less than the required amount. Typically, businesses, including banks, utilize their paid-in capital to grow their business and therefore earn more money. The 6% dividend is simply to recompense the national bank for having to give up a portion of their paid in capital. There are 1,290 national banks in the U.S. As a rough calculation, the average dividend was $1.2 million.
BTW, contrary to what another poster stated, the value of the Federal Reserve district bank stock is $100 per share as set by law. See 12 USC 287
http://uscode.house.gov/download/pls/12C3.txt