Net returns received by investors is net of cost. There are many types of costs. Some are clear, some are hidden. Our financial system is complex. There are too many middlemen, the leftover returns for the common man can be too little to sustain savings. Investors (you) becomes the bottom of the priority list.
Investors commit money and get exposed to risk. If the market moves in your direction, the hedge fund manager takes a large chunk of your wins. If the market moves against your direction, the manager is insulated from losses. He still takes a fee from you.
Benjamin Graham said that anyone can design a strong portfolio with just stocks and bonds that are representative of the market.
A doing nothing policy is always better than an active strategy. As long as you make a decision to move money, someone charges a fee. If I may summarize, always invest with the lowest cost instrument - index funds.