In a perfectly competitive market, all profits have been competed away. Economists call this normal. Economists explain it like this. Say you are making a profit selling used paper back books on Ebay. Someone will see you making a profit, and they will start selling books as well. This increases the supply of paper back books and decreases the price. When the price decreases to the point where no one is making a profit, no one enters the market and those left are making a normal profit.
In the movie "21", the MIT students are shown making a killing by counting cards in Blackjack. What is the reality? If someone is making that much money, others will enter the market and compete profits away.
Newsweek reports that those who are able to count cards make a 1% return on investment. This is hardly enough to attract new participants into the market. In Las Vegas, if the house sees you counting cards, you are asked politely to leave. Blackjack is an odd equilibrium to me. It combines skill with unfavorable risk. I am risk-averse. It seems to me that more money could me made investing in T-bills.