On the topic of found vs made materials: I’ve read that shipwrecks are getting mined as a source of steel because it’s more or less impossible to make new steel that isn’t contaminated by trace amounts of radiation from 20th century nuclear testing. While not a problem for skyscrapers, certain lab equipment requires the relatively more rare variety of found steel.
The same effect was also used in understanding brain development by looking at Carbon isotopes in brains of people born before WW2 to determine which cells were formed when.
It's almost a bit unnerving.
https://primitivetechnology.wordpress.com/2016/07/29/forge-b...
So there are something like six or seven orders of magnitude over which "high-tech" machinery can increase your iron productivity, or, to look at it another way, over which the price of iron can vary even once you have the know-how.