I disagree with your assessment, Tenebrus. The raw materials of crafting (in this case, gold and XP) are fungible. As long as there is enough such materials to go around, anything they produce should be about as available as anything else of the same or similar cost. The only reason for a crafter to make more of one type than the other is demand; there's no point in making an item to sell if nobody will buy it. But as long as there are mages willing and able to craft and others willing to pay for the crafted items, there will be enough of all of the possible items (or not enough, or too much, but either way there will be a similar availability from one magical commodity to the next).
Demand includes the willingness to sell. Most commodities like apples or swords don't involve investing your life force into it.
I'm trying to get to a balance point, so bear with me and look at this as something that could be possible rather than something that is the most possible. Think about your mage character, or the mage in your group. They take the item creation feat, rather than Superior Improved Favored Metamagic of Doom, and start putting in gold and XP. In your experience, what do they actually make? My experience is of our party cleric, who made some stuff for the fighters and made himself a hellracious holy symbol that did tons of stuff for him (and thus, for us; he was the cleric, after all). He would never sell that item. Nor do I think he would make anything for anyone else.
I'm not saying this is a model of commerce that resembles the real world. I'm saying that it is a rationale that accomplishes something good for the game. Is there general support for the goals supported by this proposal, i.e., restraining casters from getting Swiss army items to fill out their repertoire?
Happy to hear more of the critique.
That's why I the idea of mages only being able to use magic items with a CL higher than their own is appealing (provided you're able to voluntarily lower your CL for the day while preparing spells).
Suddenly, magic items geared towards casters are almost only made for your apprentice!
I'm also warming to this idea. Not sure I could sell the "your magical aura overwhelms the item" argument, though. Oh, I'd try, but not sure I'd succeed.