That seems too fast for the browser to actually refresh the page. Are you somehow just churning in the cache?
LOL. you're right. i guess it seems faster when your in the moment. but actually for shits and giggles, i counted how many times i could do it in a minute and the number was 49-ish.
i use google chrome on an open enterprise connection. (i work in IT)
i click the mouse before the "add to cart" is displayed. i know... it's tricky.
i was one of the "script guys", but found i was faster putting in the CC info myself. (i tested it against the MFC that was available)