From my understanding, The knock out call (down and out call) can be replicated by long one vanilla call with the same strike K1 and short a symetrical put K2 with ratio of square root of k1/k2 puts for one call, the barrier is the geometric average of k1 and k2. If in a positive skew, then the put should be cheaper than the call, right? Hence, overall the risk reversal costs more than in a flat skew, so why the regular knock out call are cheaper than in a flat skew?

many thanks