I thought that you were saying something other than this. I misunderstood.
Something that I am curious about... In the games that you (general you) run, would it be possible (or likely) for a PC to be able to negotiate with a specific NPC to get a particular item. i.e. Can PC Drake, go chat up Archibald the wizard, and commission a ring of protection, for instance (assuming that the wizard Archibald is capable of creating such an item and appropriate terms can be negotiated)?
This is one method by which I allow characters to gain access to items. They negotiate a price (which usually also includes some sort of a side-adventure) with an NPC spellcaster that they know and trust. After paying the price and doing whatever else is necessary, the npc makes the item for them.
There's nothing wrong with trying to find or have made any item at all. Finding someone who can make it may be an issue.
One way to limit the "Wizmart" aspect of a game (and I do believe it should be limited) is to look at one specific aspect of custom item creation: The strictly limited supply of EXP available to NPCs.
While this probably deserves it's own topic, I'll give a brief overview.
Presume a city, a county seat if you will (as in, the city where the ruling Count resides). Presume a modest number of item crafters, appropriate to the size of the city as laid out in the rules. Presume also that the ruling Count also has issues to deal with, issues that will occasionally require magic scrolls, healing potions, wands and other magic items. Like any consumable resource, he'll want to stockpile a few to help with that next border war, monstrous raid, or perhaps to hand out as rewards the next time he has to hire some adventurers.
In tense times, his demand for magic items will probably consume a good amount of the available EXP the resident magic types are able to earn through RP encounters (since they're not adventuring, killing monsters, or doing other dangerous undertakings that normally accelerate EXP accumulation.
So, how much does that leave for their "regular customer"? For their own advancement, or private projects?
Now along comes an adventurer, someone from another land who owes no allegiance to this city or it's people, and he wants to commission a high priced (and therefore high EXP) item.
Does said adventurer need permission from the local authorities, the church or the Count himself to divert so much of the artificer's limited energies to their private project?
For most in-town types, during peace time, how many actual challenges do they face? At 50 Exp per character level per significant RP encounter, it could take such a person a long time to save up enough to make your Ring of Protection from Self or Staff of Ultimate Niftiness. Even longer if a significant amount of that Exp is already earmarked for the Count's pet project.
I find it a good idea to essentially give such people a budget. Crafting the item you want may only take a few days, by the book, but it might take him a month to get enough EXP together to finish it. He only earns X amount per week, after all, and the Count has an order already in progress. You'll just have to wait your turn...