Adding HD to Homunculus

Question

My PC (Artifacer, now 6th level) has an existing Iron Defender. It was the bare minimum build for the homunculus, which I believe is 2 HD.

If I want to increase the HD to 3, the Eberron book says that it increases the build by 2,000 GP. Does that also increase the experience point cost? Is it "spend 2,000 GP and the Hit Dice goes up by 1," do I need to spend 80 XP (2000 * .04) as well, or do I have to build a completely new homunculus with 3 Hit Dice?

Answer 1

Eberron Campaign Setting pg. 32

Artificer

Craft Homunculus (Ex)

An artificer can also upgrade an existing homunculus that he owns, adding 1 Hit Die at a cost of 2,000 gp and 160 XP.

It’s 160 XP because the “base cost” of this operation is 4,000 gp: since you’re doing the work yourself, that’s halved and you also pay ½5 of the base cost (4000/25=160) in XP.