Uh,
Because they are?
Pythons shoot high velocity rounds better than S&Ws because S&W barrells are designed for the old .38 round from the early part of the last century.
My python is so accurate its hard to miss when shooting it.
I think part of that is the barrell and the other part is the action. its smooth and hand honed.
The gun is also so well balanced that in the hand, it feels like a K frame. My L frames are balanced like bricks with handles on them.
Its definitely worth paying extra for, if you want an accurate, reliable gun that handles like a K frame but soaks up recoil like an L frame.
Also it has a one piece barrel. None of that cheapo two peice barrel with sleeve crap.....