DM_Blake |
There seems to be some confusion here.
Delving is NOT a +3 (effective) armor bonus, nor is it calculated like one when determining the costs.
To calculate the price of any magical armor, simply add up the abilities that actually ARE +x abilities to get a total for the +x. Look up that price (or use the formula of x^2 * 1,000gp). Then add any flat-price abilities like Delving to the calculated cost to derive a final price.
So, for example, +4 Delving armor of Heavy Fortification would cost 91,000gp: +4 enchantment plus +5 effective value of Heavy Fortification = +9 effective bonus. 9^2 = 81 * 1,000gp = 81,000gp, + 10,000 for Delving = 91,000gp final cost (not counting the base price of the masterwork armor). This armor is effectively +9, not +12.
As Maezer said above, Delving is only on the same table as the +3 abilities so that there is a way to roll random armors with this ability (and putting it on this table instead of some other table sets the relative rarity of Delving compared to the rarities of other abilities).