Depends on what armor you're looking at how good/bad of a deal it is. Consider Light Plate, and applying the rules for Heavy Plate (which is how Medium and Heavy Plate were generated, this just lets you do it freeform). A DR 3 iron plate cuirass is $1000 and 8 lb. A DR 3 cheap iron plate cuirass is $600 and 12 lb.
Arguably it's $900 -- +50% for DR +1, -60% for cheap (the heavy plate rules are dysfunctional for several reasons).