<prompt> Human: Due to the fact that you cannot strictly predict future stock values and given that selling for higher than you paid is such an obvious goal - I always wonder if this common idiom is meant to be something of a joke. Why is it said so often if it is seemingly so meaningless?  <response>: Buy low, sell high refers more to the market price of a stock and its estimated fair value. Analysts and brokers try to estimate how much a stock is really worth and if the prediction is greater than the going market price, they buy. Obviously its a bit more complex than that but a smart brokers tries not to speculate too much because youre right. It is very hard to predict future values of stocks. 