Market dictates the price. Saotome are rare. Orikasa San lists around 200, maybe there are a hundred more I don't know but the market is limited. As Always quality, state of preservation and makers are deciding factors when matched agains willing buyers. I have seen kabotos for less but certainly there are those that cost a lot more as well.
I am sure our Saotome men; Luc, Aymeric et al can shed more light on the current market.
This particular one I was offered a month before it was made available on the Ebay but I declined.