I’m not sure that it’s an entirely closed economic system. A good number of wizards are born in Muggle families, so they have access to Muggle wealth. Imagine the Malfoys as descended from some nasty little Muggle baron (despite their ‘pureblood’ stylings) with a good head for investment.
It’s never been clear to me how the Weasleys could be poor and the Malfoys rich, given that magic seems to have not cost and wizards do not appear depleted after using magic. While one needs to buy food, it’s clear from Hagrid’s actions at the lighthouse that fire can be conjured. Much of Mrs. Weasley’s work is managed magically at home, though the addition of magicalk impediments and creatures at Grimmauld Place slows cleaning considerably.
We see at Gringott’s that wizards have a gold-based economy. We know they have valuables that are similar to Muggle valuables, and in addition there are objects of magical value. Although it’s not canon, I’ll WAG that historically some wizards earned a stipend from the Muggles they lived with (i.e., the village hag with the herbal potions, the old guy in the cave casting hexes on your neighbor’s sheep, etc.). Others provide goods and services for wizards.
In Le Guin’s Earthsea books, the wizards have Muggle-like jobs (e.g., fishing) but also specialized magical jobs (e.g., windworking). Many of higher status appear to work in the rulers’ courts, meaning they are ultimately supported by peasant labor. Also, the house-elves are slave-labor for either services or production of goods.
Wizard jobs: Professor, groundkeeper, caretaker, medical, shopkeeper, inventor, candymaker, politician, auror, bus driver, bus attendant, train conductor (presumably), trolley-pusher, cursebreaker, dragontrainer, executioner, potionmaker, lawyer/judge (informal?), receptionist, wandmaker, artisan, innkeeper, musician, newspaper writer, trainer of security trolls, Muggle liaison, and others. Many jobs are implied by the existence of, say, parchment and pens.
It is not clear to me that the Potters were aurors. Anyone have a cite?
The woeful lack of career education and services at Hogwarts inspired me to write a critique and suggestions for improvement. It will appear as a chapter in The Psychology of Harry Potter: An Unauthorized Examination of the Boy Who Lived from BenBella Books, forthcoming next summer.
I look forward to that book-I’m impressed!
but I am also the kind of nitpicky person who after the fact is strangely compelled to plot out detailed strategies for Arthur Weasley to be more successful at work.