Here I'm thinking about fantasy games, fantasy fiction, and gaming in general - and GURPS in specific.
Why make magic items?
On the surface, making magic items is kind of an odd thing for a wizard. It has a time and resource cost (heck, XP cost in some versions of D&D). Magic items are vulnerable. Whatever resources you put into them is much more vulnerable to loss than investing the same resources in improving yourself. Yet they exist, they're all over the place, and wizards in fiction and game alike often stick some of their power into an external object.
I like this explanation, personally:
You have to externalize magic to multiply its power.
That is, if you want a quick and easy way to multiply your power, you take X amount of power and stick it into an external object, and get (X * Y) power in return.
You have to accept risk. Putting some of your power or your soul into an external object is a risky thing to do. It's not safe. As much as you multiply your own strength, you now have a vulnerable weak point that can be attacked, exploited, and used to defeat you.
But no one becomes a world-dominating wizard by avoiding risks. Magic is inherently risky. Summon demons to do your bidding is risky. Selling your soul is risky. But they all come with great upsides. The talented types who fear risk don't ever amount to all of that much on the world stage. They're upstaged by the risk takers whose bets pay off.
GURPS and Champions both do this well - having an external focus for your powers makes them cheaper. Turned around, this means you can do a lot more with 50 points in a wand, staff, ring, etc. because the powers you buy come at a discount.
What about GURPS DF?
One way to do this in DF is pretty simple - allow gadget-based limitations for purchased advantages for spellcasters. Just straight-out allow purchase - a wizard with Magery 3 who wants to stick Magery 4-6 in his staff can buy those levels for 30 points, with the following limitations:
Breakable (DR 4, HP 12): -15%
SM -3 (it's -3 to hit in combat, per p B400): -15%
Can Be Stolen (with a Quick Contest) (and used): -30%
Power Source (Magical): -10%
30 x 30% = 9 points.
Heck, make it unique (for the really brave) and it's -95%, capped at -80%, or 6 points.
6 or 9 points for 3 levels of Magery.
Or get +4 Will in a tiny (-9 SM) unbreakable (DR 26+) gemstone that can only be stolen with trickery or stealth (-20%), that depends on mana levels (-10%). Cost drops from 20 to 14. Not a bad discount for a Gem of Will +4 that you stick into a pocket under your armor and wear around.
You can charge in-game for the items, too, if you like - set a cost minimum for each point. I'd just reverse the Power Items chart from DF1 and say the cost listed for an X point power item is the cost for an X character point gadget.
But you don't need to - sure, wizards might go carrying plain rocks with magic in them, but the temptation to double up and put a piece of your soul, or your next 3 levels of Magery, or +4 points of Will, or whatever in the same amulet that acts as your 20 point power item is strong. Only one thing to protect . . .
I'd stack costs if I did that - an item with a net 20 point cost advantage and a net 5 would need a 25-point item's value to contain both.
The upside of this is that PC mages have an incentive to make magic items, but aren't really in competition with NPC enchanters. They have an incentive to externalize some of their power and thus be a whole lot more powerful in return for some risk.
I haven't tried this, just run the numbers. It seems like it would be a flavorful way to have wizard PCs develop, make for really interesting wizard NPCs (he's a major foe, unless you get his amulet away), and meshes nicely with spells as powers. It does mean PC mages will get more powerful more quickly . . . and you can't give access to this kind of limitation unless you seriously mean to threaten it. A staff of Magery 3 that never gets struck, never dropped, and never threatened with theft is just a free discount on Magery 3.