Pharaxis provided you with 2 links that answer your question with at least a few dozen examples in Western literature alone.
Since you didn't read them, I will skip over the details somewhat and note that the examples provided almost all date from fantasy or pulp literature written post 1900.
Half-true, and uncivil in the assumption. Pharaxis provided excellent links, in an excellent post, which arrived while I was writing my immediately-previous; I only saw his post after I had sent mine. As soon as Pharaxis's post appeared before me, I read it, and followed the links and read the linked pages.
(There may be more excellent contributions being posted as I write this. Gimme more than an hour to catch up, please, before you judge this one as ignoring those others?)
"The Bazzar of the Bizzare" is a heroic fantasy story, in which heroic adventurers don't spend loot to buy any (usable, real) magic items. Have you read it?
And it's just about the only heroic fantasy story on the list which pre-dates the first editions of D&D. "The Goblin Market" is not heroic fantasy - that is, there are no heroic adventurer characters in the poem - and it doesn't involve anyone spending piles of loot, nor buying usable magic items such as swords or scrolls.
Thaum-Mart in 3E, 4E and 5E is based on shops in NetHack, Legend of Zelda, and Elder Scrolls, more than on anything written on paper before 1971. Diagon Alley, and so forth, were written *after* D&D, and subsequent TRPGs and CRPGs, had developed Thaum-Mart.
"Why the difference between pre-1900 epic literature and post? Or in FRPGs? In general, the writers had radically different assumptions about the origins and ubiquity of magic items."
That's an interesting idea. Yes, the Industrial Revolution changed how people thought about production of tools. Tolkien and similar writers, however, were writing in settings which were intentionally non-industrial. In JRRT's case, pointedly non-industrial, except where Saruman was involved, and for all Saruman's smoke and noise, he never replicated the palantir. (Which is significant: if he COULD have reverse-engineered and mass-produced them, then he might not have minded Grima throwing palantirs at Gandalf.) There aren't any Sword +1 factories in Lahkmar, nor in Conan's setting, nor in Earthsea, nor in "Three Hearts and Three Lions", nor in "Nine Princes in Amber". Cortana is a unique item; it's not the only magic sword in the world, it presumably co-exists with Excalibur, Durandal and Gram, but it's handcrafted, not factory-produced. So is Grayswandir - which isn't from a divine source, unless you consider Dworkin divine.
In NetHack, a Lawful adventurer can find Excalibur in a fountain, and any of the named swords can be given when one sacrifices at an altar. But otherwise, CRPG adventurers tend to find magic items as if they were mass-produced, rather than any of the story-intensive unique-named-item ways such as pulled from a tree or a stone, given by the Jedi hermit who's been watching over you since your birth, reforged at Rivendell, etc. So I don't think it's the Industrial Revolution; it's the Information Age. It's CRPGs.
Another link to TVTropes:
http://tvtropes.org/pmwiki/pmwiki.php/Main/ShopliftAndDie
All the examples are from CRPGs (or similar computer games). Thaum-Mart *without* ShopliftAndDie, in murder-hobo TRPG or CRPG, is basically "here's a free pile of magic items".
Running your TRPG as an emulation of a CRPG isn't necessarily bad. If you'd like to play a hack&slash, all the time or for occasional variety, then you could do a passable TRPG of Nethack's Dungeons of Doom, and the DM might have fun role-playing the Nemesis Quest characters.
I'm just saying, if it's your fundamental assumption that gold coin loot is all about buying magic items, then you're turning your back on the whole genre of pre-D&D heroic fantasy, to emulate CRPGs, and I'd rather you do so as a conscious decision, aware of some alternatives, doing whatever's most fun for you.