Sorqite economy; Derivations from other science-fantasy settings

A friend on discord has peppered us with quæries regarding SORQ, an ancient world irradiated with outpourings from other planes, a world of peace and prosperity for all those who live in civilized lands along the equatorial sea and within the great walls separating decency from barbarous wastes. This pestering waxes productive, and haply we shall post our outsquoze thoughts.

Let it be said that we have never once considered how money works, or if indeed there be fiat currency, and yet this was asked of us! O heavens, that's a good un init?

One of the axioms of Sorq is that it is home to very old, cosmopolitan, sophisticated civilization. The surface world along the equator is mostly peaceful, mostly equitable. There are robust civil societies, courts, mediation; basically no warfare or overt striving on the surface and inside the great walls around the equatorial zone. There are abundant trade networks and nearly universal prosperity: it is not as who should say a post scarcity civilization because the Œcumene exists in constant tension with multiple zones of privation: outside of the Walls, with northern and southern hemispheres home to diverse threats to the civilized order; the Underworld, which is rich in magical resources but full of threats to the surface; and the Translunar Realm, beyond the seven guardian moons and under the fitful glare of Bale, the old red sun.

Beyond, under, and above: each boundary to the Œcumene requires infrastructure, attention, vigilance, and violence; the city-states, leagues, temple networks, and coronal lands of Sorq cannot consider themselves beyond scarcity when so much of their substance must defend against existential threats.

Basic necessities—clean running water, shelter, food, culture, knowledge, modes of security—are in part safeguarded by enchantments and bindings in every city, temple, fane, and high place, whereby the magical emanations from other planes of existence shake down into usable power. That leaves much room for markets, finance, banking, and exchange of this or that resource or service. 

Sorqite cities use money in the form of credit, or units of account, and cash tokens. Coins are minted of fine metals or beautiful alchemical crystal, but the material of their fabrication is not their source of value: gold, iridium, and palladium coins, melted down into simple metal, become mere pretty metal, good for baubles and decoration, but worth far less than coins crafted by the ancient and scrupulous banks of Sorq.