It isn't listed in the rare skin topic, but according to the logic that a "+15% vs hexed foes" crystalline sword is about 1/20th of the price of a 15^50 crystalline sword (as it is with req 8 & 9), i'd say about 100K-200K.
But that's just a -somewhat- wild guess, so don't take my word for it.
100-200k is nothing for that swords, the prices of crystallines rizes like hell, they give like 200k only for a purple cryst sword , sometimes without a decent dmg mod imo your swor dis worth like 400-600 k