But you're talking about two different things. In the case of an iPod, you're basing its value (at least partially) on its utility, much of which is very subjective. In the case of the stock, since it has no inherent utility, you have nothing to base the real value on besides the amount of money it pays out to its investors over time, including dividends and whatever happens with the final disposition of the company. You cannot know that value until the stock no longer exists, so people speculate what that ultimate value will be and try to buy for less than that.

To be clear, I totally agree with you that the current market price of the company is determined by the stock price. But what that piece of stock is ultimately worth is a different amount.

There is a difference between cost and value. The stock market tries to make the cost equal the value, but it's not exact. Let's take the example of a company that was at one time trading for $20 a share, but gets bought out for cash at $1 a share. Those people who bought at $20 paid fair market value at the time. But they ultimately only recieved $1 back. The cost was $20, but they bought something that had an ultimate value of $1. (It's possible that that might be advantageous to them after the fact for some reason -- taxes, probably -- but on its own, it shows that cost and value are not the same thing.)