Somewhat stupid question about higher stakes HU games (LC)

[Alex/Mugaaz]

How do they play that fast? I constantly see people betting so fast that their bet is out before the flop card graphics are fully spread. Then you'll see where it gets bet, raised, and 3 bet in under a second. Higher games usually go a lot faster since people know what they are doing, but this is almost beyond comprehension. I can't see how anyone can be playing even close to their best at that speed.