Cost of Championship Kha'Zix Set when you already bought Championship Kha'Zix

I think about buying Cs Kha'Zix seperate cause I'm not having the RP for the whole Championship Kha'Zix Set jet(with the border, Icon, Ward) So i would buy Cs Kha'Zix for 1350RP and now im wondering how much the Set costs when i own the Skin. I wonder how expensive the Set will be.

So, if someone only bought the Championship Kha'Zix Skin, could he please tell me how much the Set costs for him? Would appreciate ^^