Hunting for the bike shop article to see if I just imagined it and found a page full of marble news which mentioned that 1/2 inch was a popular size for steelies in 1928 ... fwiw.
And the auto salvage guy donated 24 steelies for tourney prizes. Said they were valued at 6 cents each.
Another stray, useless, tangential thought ... I don't know how it would have been calculated or paid to him ... but didn't Martin Christensen retain the right to part of the profits for steel balls made after he sold his patent for making them, back around 1900? It was said he only sold 80% of the patent. I can't remember if I've seen anyone explain how that arrangement worked. But it secured his family's financial future before he started on his marble making venture.