The Ongoing Phenomenon of Unsellable Elites & Elites Priced Ridiculously High

The transactions are not player to player and the "bot" acts as a middleman for the transactions. There are multiple auction house servers, thus explains why you may not have seen your brother's listing. The actual supply and demand of pricing is controlled by the players though. If the Kareem Hunt sold for 1 million coins, players should be able to successfully list the item for a price around that range. If they do not sell, it's encouraged to lower the price of the item until a new buyer sells it to establish it's true price.