Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why do investors buy stock that had appreciated?
I understand you make money by buying low and selling high. You can also make money by buying high and selling higher, short selling high and buying back low, short selling low and buying back even lower. An important technique followed by many technical traders and investors is to alway trade with the trend - so if the shares are trending up you go long (buy to open and sell to close); if the shares are trending down you go short (sell to open and buy to close). "But even if the stock price goes up, why are we guaranteed that there is some demand for it?"  There is never any guarantees in investing or trading. The only guarantee in life is death, but that's a different subject. There is always some demand for a share or else the share price would be zero or it would never sell, i.e zero liquidity. There are many reasons why there could be demand for a rising share price - fundamental analysis could indicated that the shares are valued much higher than the current price; technical analysis could indicate that the trend will continue; greed could get the better of peoples' emotion where they think all my freinds are making money from this stock so I should buy it too (just to name a few). "After all, it's more expensive now." What determines if a stock is expensive? As Joe mentioned, was Apple expensive at $100? People who bought it at $50 might think so, but people who bought at $600+ would think $100 is very cheap. On the other hand a penny stock may be expensive at $0.20. "It would make sense if we can sell the stock back into the company for our share of the earnings, but why would other investors want it when the price has gone up?" You don't sell your stocks back to the company for a share of the earnings (unless the company has a share-buy-back arrangement in place), you get a share of the earnings by getting the dividends the company distributes to shareholders. Other investor would want to buy the stock when the price has gone up because they think it will go up further and they can make some money out of it. Some of the reasons for this are explained above.