I'm not sure if you're a not but. Your argument would mean that mining more copper out of the ground wouldn't cause the price of copper to drop (the other side of the coin of prices of everything else going up) cause there's no seigniorage. It was all supply demand.
Discussion
that's right. it's a product of the free market. mining more copper out of the ground doesn't cause price inflation. due to the free market and diminishing returns (remember, it's a market, not a monopoly) the copper mines cannot profit through seignorage and only dig up copper when there's market demand. digging up copper requires proof of work (you have to pay for energy consumption, machines, tools, workers). you don't profit from any seigniorage. you dig for it because there is market demand which you clear by digging up copper. and by investing your money in digging copper (and not spending it on other products which would cause prices to rise) you haven't caused any inflation at all.
It still devalues copper.
If your pricing things in copper all your prices have increased.
not increased, but stable, which is what you would expect from money. prices would only increase in very rare situations where you suddenly and unexpectedly experience an event like a massive amount of extraterrestrial copper entering into the earth atmosphere. bitcoin and monero don't suffer from this as long as the monetary policy stays untouched. both in btc and xmr the monetary policy is known to everyone in advance who voluntarily enters the system. and since monero inflates only in absolute terms (0.6 instead of let's say 0.6%) both systems have hard caps in the long term. even xmr people don't seem to understand that having an absolute number of unit inflation is no inflation at all in the long run.