Using that logic you could say it's never worth buying anything. A loaf of bread costs the fully-loaded expected value of that loaf, so it's never worth buying a loaf of bread because it's always going to be worth exactly what you paid for it. But actually trade is a wealth creation mechanism because different people put different value on things: to you the loaf is worth more than the money you paid for it, while to the shopkeeper the money is worth more than the loaf.

The stock will cost a fair market-clearing price for its expected return, risk-adjusted. But often a stock, or a perpetuity, is a good purchase for one or other market participant - no different from a loaf of bread bought at a fair market-clearing price.