Do you really think that casters have nothing better to do than craft magic items for sale? Wizards (for example) have better things to do... studying, rivalries...etc than sit at a desk churning out items for profit.
Read my analysis again. Of all those who are high enough level to have item creation feats, only one-fourth are considered to actually have them, only one-half of those actively use them, and even they only craft an item once every *six months*. Assuming that the "average" item is, say, a +1 weapon, it takes 16 hours every six months to craft items at a rate which would produce the plethora of items outlined. It's a vastly conservative estimate.
I spend more time in the shower than the "item creator" wizard spends crafting under this line of analysis, and I've never been described as "having nothing better to do than sit in the shower all day". This is not a magical item factory. Wizards are not constantly churning out items. I'd say that spending 16 hours every six months crafting items is not exactly some sort of constant shackling to their item creation lab. They have more than enough time (i.e. all but four days in the year) to pursue other interests.
The idea that every soldier, nobleman, rogue, tavernkeeper and priest has magic items makes no sense, and defies logic more than my opinion
That's patently not the case. Not evey soldier, rogue, tavernkeeper and priest can afford to fork out 2,000gp for a permanent magical item. That's twice as much as an average house, or sixty years' wages for an average peasant. They might be available, but they're not cheap. Just because Ferraris, LearJets , luxury yachts, deluxe holiday homes and cruise missiles can be obtained for cash, it doesn't mean that everyone has them.
Some wizards pay for food with the tried and true methiod: "Not setting you on fire."
Does every fighter earn his keep by "not beating you up"? Does every rogue earn his living by "not robbing you"? No? Then why should every wizard hold the world to ransom. For one, no good or probably no neutral wizard would earn his living from blatant extortion. Secondly, large cities would have authorties to deal with this sort of thing; and smaller settlements occasionally put out for groups of "adventurers" to remedy such situations

. Sure, some might earn their living this way; like I've said, I'm only taking one in eight spellcasters to have and practise item creation feats. That's not exactly all of them.
So by your book, every wizard in the world sits there churning out magic items?
I think I've dealt with this.
I never said that NO wizard ever took gold for a magic item, just that 99% of those who can have better things to do with their time then churn out +1 longswords for every punk kid who comes along.
Alternately, 87.5% have better things to do than produce a +1 longsword every six months

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Making something for sale commodifies it. Shopping is not heroic. Purchase of magic items isn't part of any genre I want to emulate.
Sure, but it's realistic. If the PCs want to buy a ship or whatever, they can presumably acquire one with relative ease for a simple exchange of money. This isn't about "heroism". It's about allowing a campaign world to act in a realistic fashion. It's about verisimilitude.
These assertions that capitalist dogma should hold true in fantasy worlds are quite bizarre.
It's the default assumption in DnD. You could make a socialist world, but it would be strange (socialism relies on a huge modernised bureaucracy) and non-core. The entire canon DnD is premised upon capitalism as the mode of economic exchange, and this is also true of all WotC-published campaign worlds.
Of course there's nothing wrong with deviating from the RAW, so long as you're clear and up front about it. In the DnD world I'm writing at the moment, there are no magic shops. In fact, characters can't even take item creation feats apart from Scribe Scroll and Brew Potion. That's my world though and it deviates sightly from the default. I've argued the pro-trade in magic items case as I find all of the arguments against it existing in typical DnD settings to be implausible.
Precisely. This argument isn't about campaign flavour or world-building. It's about logical deductions given certain premises. I've nothing against people like Ibram who wish to build alternate Lovecraftian magic systems, or Doug who prefers a low-magic world, but this argument is about whether, in canon DnD and given canon assumptions, there would be magic shops. It seems quite clearly that there will be.