This is one of the reason why Bitcoin is better to buy things rather than other currency. As promotional price as to introduce bitcoin, several online shop give discounts to those who pay them with Bitcoin. Another thing is that using Bitcoin doesn't require you to send all your personal info including visa card or credit card.
That is another huge plus with using bitcoin. You don't have to worry that Amazon/Ebay/Etc. are going to keep your credit card information safe. You don't even have to give any personal information, just send the right amount of bitcoin to the merchant and everyone is happy. You get your stuff, and they get their money.
and the seller will know it fast also that you have sent payement already,right?