You almost defined the P/E - the price earning ratio. Usually, a stock is worth around the order of 10 to 20 times the yearly earnings of the company. If you take all AAPL stocks, their value is around 17 years of earnings. P/E can be higher when investors expect the company to grow in the next years and so soon generate more revenue. An example is Amazon with a stellar P/E of 94. Don't know how long they will sustain that.