Perhaps they should rewrite the code; first obliterate all masked out, then do light calculations, etc.
But Sjefen, that's what the guy told me too, faster as mesh without alpha, but with alpha it needs more translucency to get rid of dark plant centers, which costs.
Some leaves are so complex that a tight mesh can't be made, so you need an additional alpha, as Steve pointed out too, so I wonder if just a little alpha (black) would cost as much as a lot more alpha...
But anyway, my question has been answered, thanks all.