So, VERY roughly, Platinum is $10,500 a pound, gold is $13,000 a pound, tungsten is $75 a pound. And lead shot is $10 a pound. And steel is pretty much free.
And apparently, if you're the right person in the right place at the right time, depleted uranium is/was about $3 a pound. But, let's face it, you're not.
I will tend to weight my boxcars with steel.
I will tend to weight my locomotives and some open cars with lead. Sheet or shot.
And I expect, someday, to buy a pound of tungsten powder for that exceptionally special locomotive and/or freight car. In particular, I have in mind a diesel switcher that PULLS.
Though that platinum is kind of tempting.