Looking back on my childhood, I heard a lot of economically absurd statements. But I didn't recognize them as absurd at the time. Teachers and parents said stuff, and I believed them.
The first time I encountered economic absurdity and knew on the spot that something was awry: I was eleven years old and reading the Dungeon Masters Guide (first edition - yes, I'm old!). Background: In the game Dungeons and Dragons, magic-users keep their spells in books, and learn more spells by copying them from the books of other magic-users. You'd think that, in equilibrium, spells of equal power would trade roughly at par. Or maybe some would be scarce and sell for more, while others would be common and sell for less. Or maybe they'd be available for free on the magical equivalent of Kazaa.
But according to the book, player characters can only buy spells at par from each other. The rest of the world drives a far harder bargain:
Superior players will certainly cooperate; thus, spells will in all probability be exchanged between PC [player character] magic-users to some extent... This is NOT the case when PCs deal with NPC [non-player character] henchmen or hirelings. Non-player character hirelings or henchmen will ABSOLUTELY REFUSE to co-operate freely with player characters, even their own masters or mistresses... As a general rule, they will require value plus a bonus when dealing with their liege. If they will deal with other PCs (or NPCs) at all, they will require double value plus a considerable bonus.
This example - where a PC named Halfdan wants to buy a spell from an NPC named Thigru, still cracks me up:
If Halfdan has been at least civil to the magician, Thigru will ask nothing more than a third level spell in return, plus another spell, plus some minor magic item such as a set of three potions, a scroll of 3 spells, or perhaps a ring of invisibility... [S]upposing [Halfdan] had actually saved Thigru's life at one time, the cost would be reduced to but a spell exchange and a single potion or scroll of one spell.
In short: You can save someone's life, and they still refuse to trade at par. Even when I was eleven years old, that seemed more fantastic than a ring of invisibility.