Idk $50 I guess. But due to his nice colors and huge kok He will be over priced.
Good color, good kok. I bet it would bring $50 - $100, depending on the local market. There is a LFS around me with a really nice full-grown zz Red Dragon in their display tank. They claim to have turned down $500 for it. Of course, the worker that told me that claims to have cousin/uncle/friend/whatever with a Koi worth $100K.