"Elric is noted for using rare herbs and potions to maintain his energy when he is not under the influence of Stormbringer."
Another good example. Thank you again. But... is that really about adventuring, gaining gold, then spending that gold on magic items? I vaguely remember that he was the kind of person whose wealth was an assumed part of their background, and that how he paid for potions was no more an issue than how he paid for breakfast, lunch and dinner. You know those stories better than I do, so... is Elric a model for the 5E D&D character who's poring over a price list, and hoping that their next raid will yield enough gold for an armor upgrade? I mean, you've answered my late-in-the-thread sub-question, but I dunno if that also answers what gold *as adventure loot* is good for in 5E D&D, and whether gold is useless for those who have plate mail and can't find magic items for sale.
At certain points, yes, because he wanders off, leaving the throne to Yrkoon the Userper, thus abandoning the vast majority of his wealth. And even though he is still wealthy, sometimes he cannot pay for what he wants with what he has because the merchants simply cannot make change- some of the Melnibonean currency he carries is so valuable he could buy small towns with a single coin.
To that, add that he is aware of the negative influence of Stormbringer, and occasionally tries to do without it, reverting back to the potions and herbs.
"post 1900 is when magic as technology and economic commodity first appeared in literature." Yup. People didn't have the mental models, before roughly 1900. How often does it appear between 1900 and 1940, or 1945 and 1970? (You know the genre at least as well as I do, and I'm curious what you can tell me.)
"I didn't get a CPRG of any kind until 1984, the first Wizardry game. Yet I've personally run campaigns with magic shops of some kind or another since at least 1980 or so. And the concept didn't originate with me, either- I encountered it as a player in games run by others."
So where *does* it originate? How plausible is it, that those others got the idea from Izchak's Magic Lighting Shop (or some other CRPG source)? How plausible that they got it from "Bazzar of the Bizzare" (or any other published-on-paper story)? Or is there a third answer?
I doubt you'd find a single source.
I was familiar with Lieber before I picked up the dice in '77, so when the first DM told me of a magic shop, I was unsurprised that one existed.
Likewise, simply being well-read can point you in a number of directions. You can find medieval stories in which protagonists seek out witches or sorcerers with an eye towards buying potions or the services of a spellcaster to enchant someone or themselves.
Many of the oracles of the ancient world made their livings off of people paying for their prophesies.
Two people independently of each other came up with calculus; two people working separately were awarded the Nobel for their work on the creation silicon chip.
The point? Inspiration doesn't necessarily have a single source.
At this point, we're in your personal experience, totally in your wheelhouse, you're the one with the primary source; I am asking, not debating. (Well, you said that I was totally wrong, and I'm introducing a theory in which I might be not so wrong, but I'm pointing out a gap in what you've said, not challenging the substance.)
I would like to know why what people expect in D&D campaigns, is *so different* than the source material which Gygax credits as having inspired the D&D setting - and why 5E PCs see gold as "useless" in a way which would have *baffled* Conan, Grey Mouser, Frodo, and Elric, as well as Arthur, Robin Hood, Beowulf and Odysseus.
Their expectations may differ from yours, but not necessarily from Gygax, et alia's ideas and inspirations. You're looking at a very truncated list of what they said were their source material was. Gygax at the very least was very familiar with Moorcock's work- the alignment system was heavily influenced by it. And again, you can find people buying magic in all kinds of faerie tales and stories from all over the world.
The games at different tables just differed on which model they preferred- rare or common magic- and went from there. The more common the magic, the more obvious the magic economy.