Value investors require some room for error in their estimation of value, and they often set their own “margin of safety,” based on their particular risk tolerance. The margin of safety principle, one of the keys to successful value investing, is based on the premise that buying stocks at bargain prices gives you a better chance at earning a profit later when you sell them. The margin of safety also makes you less likely to lose money if the stock doesn’t perform as you had expected.
Value investors use the same sort of reasoning. If a stock is worth $100 and you buy it for $66, you’ll make a profit of $34 simply by waiting for the stock’s price to rise to the $100 true value. On top of that, the company might grow and become more valuable, giving you a chance to make even more money. If the stock’s price rises to $110, you’ll make $44 since you bought the stock on sale. If you had purchased it at its full price of $100, you would only make a $10 profit.