Go read this thread.
The Size Myth In The Porn Industry
As gjurob says, there are "tricks" to make the guys look bigger than they are on video. Sure they are big, but not as big as they may appear.
Examples:
— pair him with a really petite girl = his dick looks bigger
— shoot him from below with the camera = the lens makes his dick look bigger
— shoot a closeup of his dick from the side where is dick is right next to the camera and the girl’s face is a foot or so back = the lens makes his dick look bigger. The close side view shot makes things look bigger anyway.
— a 5 foot six inch guy with a 7.5 inch dick on video = our brain scales him up to a 5 foot 10 inch guy with a 9 inch dick
If you don’t have time to read it all today, then skip to this post:
Krod - The Size Myth In The Porn Industry
Krod found some pictures of a porn star who is claimed to be 9" or 9.5" being measured against a wrench that is known to be 6". You will see objectively that there is no way he can be that size. He is probably very skinny and not too tall, and our brains are scaling it up again. This guy is featured regularly in those "Porn Stars Like It Big" episodes.