Well, my suggestion actually was on the line of logic that ALT should not highlight some items that are very "valuable" in terms of their use, rather then any economic value - specifically the various keys that open important closed doors or traps or locked important loot chests.
Those are usually right in the vicinity of those doors and loot containers, so it feels like a bit of a cheat to so easily find them with ALT key.
If it was tied to perception then the players who invested in it would have that small additional reward available, while others would have to pixel hunt a bit more.
Other, normal loot items would not be affected by this and alt key would highlight them all as it does now.
