text: how much does a stock option cost? is it a percentage of the stock price? let's say i buy a call on some shares of apple computers. how much?  if i decide to exercise the option and buy the stock, do i pay brokerage fees again? each option entitles the owner to buy or sell 100 shares of the underlying stock.  option pricing depends on several factors.  strike price of the option, volatility and time to expiry.  options are a separate transaction and do require another commission if it is exercised. .