Its not for the same price...if Villain starts betting the pot or 3/4 the pot on turn and river, you're paying MUCH more than you would if you 3-bet the flop first. In addition, you STILL don't know where you are, unless you raise the turn.

Plus, the Fold Equity on the flop is pretty high imo. You're beaten by 3 hands, but there are alot more than 3 hands that would min-raise the flop in late position.

The amount of money you gain when someone folds, plus the money you save when you are actually beaten, makes 3-betting a good option, at least thats what I think.