[Thomashuet]

The main problem with this is that we're looking at the evolution of inflation-adjusted prices for common ressources. By definition, inflation-adjusted prices for common ressources must be constant, that's how we measure inflation. So it shouldn't come as a surprise that the prices do not change much in the long term.

[choeger]

That's obviously wrong. If one resource gets scarce but retains its use, it will get more expensive compared to other resources that remain plentiful.

All commodities together feed into inflation. So either some will become less expensive or some will outpace inflation.

What we're seeing here is that resource extraction can get better, so resources aren't really scarce. But there are certainly some commodities, not reflected here, that became much cheaper. E.g., corn or meat, so these metals might have become more expensive in relative terms.

[dredmorbius]

I think you're right that the underlying problem is the economic theory and behaviour of nonrenewable resources. Or more accurately, the utter lack of correspondence between economic theory (Hotelling's Rule) and actual price behaviour.

This isn't a matter of inflation but of the lack of accounting for the fact that nonrenewable resource are, well, nonrenewable. Unlike (at a first blush) farming or labour, where utilisation currently doesn't mean that the same resource is unavailable in the future, once a nonrenewable resource is extracted and used, that production process cannot be run again.

Metals and ores can of course be recycled or reused, though in practice achieved rates are quite low (50% is exceptional, and that means that 1/32nd of the original resource is available after five cycles). Fuels which are combusted are a whole 'nother matter, as once burnt (or fissioned, in the case of nuclear power), the resource has been degraded and won't reform in anything less than geological time, if ever.

Once one comes to face with the fact that we're utilising fossil fuels at ~1--10 million times their rate of formation, the problem and inadequacy of economic pricing models becomes glaringly apparent.

Metal ores may recycle in less time, and some (e.g., iron) are massively abundant. But, again in the case of iron, when one considers that commercially viable ore deposits were formed 1--3 billion years ago, during the first phases of life on Earth, and driven by those biological processes.