In the flea market, we can only sell items and buy what is currently available for sale by other users.
But I think we should have an alternative option to trade in the fleamarket. Same as with pebbles and moonstones, you can sell either one for the other. We should be able to list requests for specific things and how much we are willing to pay for it.
Obviously, this would not work for wolves. But users should be able to set up trades like "I'm buying 100 bananas for 50k pebbles" and another user can fill in the 100 bananas, instead of making a separate listing if they think they'd rather get the 50k now rather than wait a week for a potentially better sale.
When selling items, players should also have easy access to check the item they intend to sell if there are already listings to buy it.
When browsing items you should see both selling and buying listings side by side. Obviously you should be able to filter between one and the other.