With the single currency and the single monetary policy it is no longer possible to use currency devaluation to offset productivity differentials or real appreciations resulting from inflation differences and to restore the competitiveness and employment of a given economy.
These trends appear to reflect primarily major increases in supply, with some moderation in demand playing a role. That would appear to be the case for iron ore and oil prices (and, prospectively, liquefied natural gas prices, which are typically tied to oil prices). Base metals prices, where few significant supply changes have occurred, have fallen by much less.