Currently, it is very difficult to figure out the worth of an item or UV in Spiral Knights. There's no resource for getting a ballpark figure, so you are left to asking around. I see a lot of predatory traders who rip off new players, buying their items well below market value and reselling it. This is not a good situation, and it certainly isn't encouraging those players to stick around. However, it is easily fixed.
Let players search the Auction House for completed auctions. That way, a player can see what prices similar items have sold (or failed to sell) at in the past, and have a rough estimate of their item's value. Even if the auction history only goes back a week or so, at least it gives a good ballpark figure.
Going hand-in-hand with this, I think the auction house should have better search filters. You can search by UVs, but that just checks whether they have them at all. I'd love the option to search for "Just Max" or "only Attack Speed Increase".
You do realize that weeks worth of data would take at least an hour to sort through, even if you knew what you were looking for. Its good in theory, but a lot players don't seem to have the patience for it, and even fewer being able to correctly read the trends. There would need to be a way to streamline some of the information to make it easier to digest... but I'm leery of resorting to an average price index with UVs being a heavy factor, and separating by UV and level would have a lack of samples on certain rarer types.
Despite the above, I'm all for better filters in the listings.