(ref: http://en.wikipedia.org/wiki/Money_in_Harry_Potter#Economy)
(ref: http://en.wikipedia.org/wiki/Money_in_Harry_Potter#Economy)
Economics is a real spoilsport for fantasy literature. I was once taught a single sentence which now nags at me in every book I read: "Describe how this army is fed." For example, the carnivorous Canim in the Furies of Calderon series fielded an army of some 60,000 apex predators in a sparsely populated agricultural region for a period of over two years. Their purchasing agent should require about as many sources of meat as all the McDonalds nationwide, but the economy as depicted couldn't possibly support that.
http://en.wikipedia.org/wiki/Charles_Stross#Merchant_Princes...
"Due to copyright restrictions, certain Kindle Titles are not available everywhere. If the country or region displayed is incorrect, you may change it by clicking "Change region"."
I could circumvent that via using my US proxy or wait until I go back for Christmas, but I really wanted a book to read on the plane ride tomorrow. And you know? Screw it. I'm going to buy from one of the numerous publishers who is willing to take the money I am attempting to throw at them.
As for Harry's parents having money, they were a highly skilled witch and wizard husband/wife team. Just as in the muggle world, as with a smart husband and wife tandem (think the Obamas), they would do well economically. Harry's money is riches for a single kid financing a few school years, not necessarily a king's sum meaning he is set for life.
Harry's parents are mysterious figures and I would guess that their wealth (or his rather) was more inherited than from being a highly skilled witch wizard team. He did inherit the invisibility cloak.
For example, something that bugged me about the re-imagined "Battlestar Galatica" series was that a group of only 38,000 survivors, apparently with no more automation technology than the real world, and under constant military threat, have a humming specialized economy. It includes arms manufacturing, ore processing, and even illegal niche industries like child prostitution. It can do these things in addition to maintaining and operating a fleet of sophisticated spacecraft, running intensive military operations, and feeding, clothing, and sheltering everyone. It usually feels more like a population of half a million than 38,000.
But some of the episodes feature shortages of labor or resources, and I like it when this happens. It seems more real. It's easier to empathize with the characters because I can better feel the bleakness of their situation and their challenges seem less contrived.
If you had enough time, effort, skill, and raw material, why would you ever need to buy clothes from the GAP, mass produced food from Safeway, or entertainment from BestBuy? Certainly, it would be cheaper and healthier to make your own food. But do you really want to spend all your time making stuff, when, overall, it would distract from what you really want to be doing with your life?
In terms of Harry Potter, there is a law of conservation occurring there. Many things 'conjured' there does not last very long, and even to get them into existence requires energy from the summoner. In fact, it specifically mentions in the last book, Harry Potter and the Deathly Hallows, Hermoine states a conservation law about why wizards can't conjure food. (Don't remember which one.)
I hope this answers your question.