One way to explain the xp loss is that the permanent infusion of magical power into an item requires an infusion of part of the animating life force and soul power of the creator.
There are plenty of legends that a maker of a magic item puts part of his soul into his creation to power it, this sets up a mechanic for that and makes it the default.
It's true that a spellcrafter can't create an infinite amount of magical items, it will always hold a personal cost to create an item under the default system.
Minor magic items, however, can be made without a feat or xp, continual flame can make an everburning torch, illusory wall can create a magical trap cover for a pit, and permanent and programmed illusions can do some neat effects. Fire traps, glyphs of warding, etc.