First off, I'd like to say that I own an expensive set of knives and they are SOOOO worth the cost over cheap knives.
Moving on. Don't think of the cost of magic items as actual "gold". Think of it as the gold equivalent in residuum to create that item. Magic items aren't mass produced by powerful casters because no one but kings, wealthy merchants, and successful guilds have the money for even one magic item. Like a pharaoh building a pyramid or a king building a great monument, a person/organization only has the wealth for 1-3 powerful magic items in a lifetime.
Magic manufacturers get a 20% bulk residuum discount, which they turn into profit. Player characters don't![]()
S'mon does put forward one possible explanation, which is that PCs are using a quick-and-dirty method to make magic items, while professional item-crafters do it offscreen using a more efficient, NPC-only method. But that leaves unanswered the question of whether you have to be 30th level to use that more efficient method.
Actually if you read PHB1 carefully what it says is that the cost to purchase an item is the base cost PLUS 10-40%. This is the merchant's markup, so it actually makes some degree of sense.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.