Selling this entire house, the key goes on its direct way to the highest defrayal
Better be adviced to not search for rares or valuables in the screenshot, it is just a storage of a random collection of nearly everything that you need for various tasks ingame. Part of this here is also a large chest, which contains a collection of all kind of potions, dusts and figurines. The treasure maps at the lower edge are lying upon another going into the hundrets of each pile.
Nonetheless, if this whole cohort was sold to the local store, the avails would probably exceed the one million platinum coin mark.
So no offers of a lesser value than at least 1500d, obviously not going to accept platinum for it. But one or another might see the true value in a collection of next to everything anyways.