Magic Weapons and Armor, how do you handle them?

[zombiehands]

I never liked the idea of giving armor DR. I think that would require a whole new armor system.
Multiplying cost makes little sense to me since you start to get strange things like Expert armor cost more than magical armor.

I do something similar to treeborn. Expert cost 1/2 of +1 or 500 gp. It gives the bonus of being +1 to hit and damage for weapon and AC for armor and shield. They don't get the magic aspect like hitting monsters that need magic weapons or resizing to the user.