Need help appraising Japanese Koi Koi

Hello, I will just start of with saying that Im not trying to sell the koi here as I already have a place to sell them, I just wanted to know what I should charge for them. My grandmother has had these Kois for as long as I can remember and she is getting too old to take care of them so she has asked me to sell them for her, they are about 500 cm long and are Genuine Japanese Koi(atleast she says so), one is white with black spots, while the other is orange with black spots too, I will try and add pictures later if needed, thank you for your timeEDIT: Ive determained the white one to be a Gin Matsuba and the Orange one to maybe be a Hi Utsuri

Most likely a private buyer, I will be using a local auction site. Here are the pictures of the two fish: