Impervious Weapon property

Its a weapon property that is listed in Ultimate Equipment however normal weapon properties are listed as costing +1 or +2 enhancement bonuses and what not which makes it obvious as to them enhancing the weapon however Impervious is listed as having a gold cost of +3000 gold.

tl;dr I am wondering does the Impervious weapon property count as a weapon enhancement or is merely strengthen the magic but doesn't add enhancement?

From my best understanding, flat cost enchantments are tracked separately from the upgrade cost. Whether the weapon is a +2 or an effective +8, Impervious would simply require 3000 gold to add.

My understanding is the same as Darkwolf's.

Indeed. Adding a flat cost enhancement to a weapon, armor, or shield does not affect its effective enhancement bonus for future enhancements.

Okay that was my understanding as well, awesome thanks guys for responding!