Storm Raven said:
And this is different from buying and selling magic items how? You are just quibbling over the mechanic of the market, not the existence of the market itself.
It's not merely arguing about the mechanic; it is arguing about the circumstances. In my model, there is no presumption that:
(a) the characters have access to an NPC who can make the item
(b) the characters are deemed worthy by the NPC to have the item made for them
(c) the NPC is inclined at the time the characters want the item to part with the xp necessary to create it
Let me express what I mean in terms of silk:
(a.i) the characters might not be in a place that is receiving silk imports
(a.ii) there might not be anyone in the characters' region capable of actually working with silk
(b.i) the characters might find a merchant with silk who is saving up his limited supply for when a noblewoman or someone else capable of showing off his product in the right circles feels inclined to purchase it
(b.ii) the characters might find a merchant who is a member of a guild that only allows the sale of aristocratic clothes to aristocrats and deems it unlawful to sell aristocratic clothes to people of no rank
(c) the tailor might be keeping this bolt of silk on display in his booth in order to attract future customers; he might therefore decide that he will become just another tailor of he gives up his one bolt of silk and becomes just like all the other tailors in town
So, the fact that there exists a silk market in the world does not automatically mean that the PCs can go out and buy themselves silk outfits.
The ability of characters to purchase magic items is conditioned by at least three factors:
(a) the existence of the item
(b) the availability of the item
(c) the values of the individual capable of obtaining the item for the characters
Or better still, how about children? Children are much more abundant than silk. The fact that it is undeniably true that people are selling children in this world does not make it true that the purchase of children is an opportunity available to everyone.