Its the issue w/ currency. Metal is something everyone needs, so in that sense its a currency that continues to grow, much like dollars. Keys are like gold (or some other commodity) and people buy it to hedge against inflation to some degree. In order to keep metal down they'd have to require people to demand more of it and either store it or take it out of circulation. Someone at one time suggested using metal for man up tickets or some such thing. It would be a good idea to do if valve wants to keep TF2 afloat. People are really just demanding less metal because there isn't much use for it. Sucks, but it is what it is. Hats can be bought on the steam market now, so no one really cares about the old craft hats.