The rules tend to be scanty because it's not a very exciting session, but the thing is, making magic objects is probably the most world-changing thing a spell-slinger can do. (Especially if the world has some sort of restriction that actually keeps them as rare as they are by rule fiat in the game.)
Not the consumable ones. A potion is not that much more useful than a spell-slinger. But if you have a recharging wand of cure light wounds, you have started to change the world. One wand here, another one there, a third there -- these things start to add up.
Some have more effects that others.
Let us suppose you have a dozen locations where the judges have a spell to compel telling the truth built into the courtroom. The effect would be enormous even if they were the cumulative effect of one high-level cleric every century or two. It's not just the cases heard there. It's the omnipresent threat that your case might end up appealed there.
A magical revolution could ensue. And just as the industrial revolution allowed for more education (because the vast majority did not need to drudge in agriculture from an earlier age), a magical revolution would produce more leveling spell-slingers as they could escape their drudgery, too.