Hope this is the right place for this, more of an oversight maybe than anything.
Your belongings will always show half the worth in shops, but when you sell something, you only get a percentage of that amount. I believe it is around the same percentage as the discount on buying at the shop. For instance, I’m at a town where small shields cost 22 crowns, and my inventory shields say 22 crowns too. But when I sell it I only get 14 crowns.