Not refuting your point but this could also change for precious metals in the mid/far future: https://en.wikipedia.org/wiki/Asteroid_mining#Scarcity

"the relative abundance of asteroidal ore gives asteroid mining the potential to provide nearly unlimited resources, which would essentially eliminate scarcity for those materials"

Apparently with the lack of a strong gravity like Earth's to sink down heavy metals, they are way more accessible in smaller bodies like asteroids (Ceres and Vesta maybe?)