@__________@! Buy 'em all!
They are actually untradeable but they have been glitched to make them tradeable. Soon there will be a rule or some other action taken to prevent this from happening.
Actually, only the ones from Boutique are Untradeable. If people have stacks of them from before the patch was implemented they havent been effected.Mine had unable to be traded on them too, and I could still put them in catshop.