Problem is, metal is free. You don't have to do anything to get it, other than play the game. There's very little use for it. Sure, you can craft a hat with 3 ref, but why pay 3 when you can buy two hats for cheaper? You can usually save anywhere between .33-1 ref, depending on how much you buy the hats for. Then the traded metal goes towards, say, buying a key. Which someone sells that person a key for 7 ref, and buys a key at a lower price, sells it for 7, and makes profit which will then eventually buy another key. See the problem? The metal isn't leaving the system, and if there's anything basic economics teaches, it's that more money makes it worthless.
We can blame it on Backpack or other pricing sources all we want, but the fact is that unless metal starts leaving, it's just going to become steadily worthless over time.
And keys are pretty much worth 7 ref at this point, or at least they sell easily at 7And I'm totally not one of those people who buys keys at 6.66 then sells them for 7 on OP successfully, nope, no way